Upload
mahmoud-ibrahim-shaker
View
83
Download
18
Embed Size (px)
Citation preview
��� ����ت ا����� و ����ت ا�� ر ؟ � ه� ا��ق ا��ه�ي —1�� ا��ه�ي ان ����ت��� ا��ق ا�� � ��� و� !���� (ا����� -,(+ &*() '&% $�# �"!
�� �� ��"�� دا2) /� ��1 ان) �'&% /���� �� ���� ا�� ر -,(+ &*() '&% /�# �"!89 �7 -� ر ا�() و� !���� '&% 456( ا�4�4 !�: ��"��) ��<4م -- 2: +�/ DIRECTIONAL RELAYJ'ا�Kه� ا ؟ ؟ و�
. directional relay ال J: ��<4م /% 1(- bus bar-generators -transformer _ J`:�aا bcوه ��<4م �*5: d over current relay
ء relayا(!J`a ا(��gع '&�5 ال ه% -�(%a2 )�� 41وث اىfault( b�� /% ا4ا (fault) ا� J ا* د:J :(� ا�� ر /% /% ا�-� b ا* دى &4ا��b و�k '!4 41وث اى /!�4 ان /%
% :(� /% ا-� b ال- ن ا-� b ا�� ر :!*lk و�/ relay �`�/م الrelay (,�� الC.B : directional relayو:��K 46'�� �� ال.
1 -- J*� 4م>�� س ا�� ر over current relay ا!�ع اcى :k*K!�ع :�,) �*4 اا اcوه ا(`!� وز: د-J '� ا�� ر
Instantaneous directional relay--2 4*� �q� (,�: !�عا اcوه س ا�� ر /�J و:��<4م �(k*Kو�6د ا J� :J ا(�4ات /% 1
��bus barl�K %&' �:4 ال3 --��&g ن ا��ds`ا �: )� �d1 ه� ا�( :� ا(,� BUSBAR DIFFRENTIAL
RELAY؟؟ :� ا��xاف ا����.)1 voltage supervision relay
؟ HVHRC ا��{ � ذا :*!% } -- 4 High Voltage High Rupturing Capacity fuse هcا ا��{ إ�2, ر ــ: ج
ت��k)ت ا :� ا(���ت و�1)� % �ت وه� :��<4م /% �1 ت ا�45 ا*� kت وا وا(��آ .ا�% -*() '&% 456 ا��"�)
ا�� ر '!4 '4م ا-, 5+ ��()؟ ( ذا :�8 $,� �/� ���ل -- 5 �� �) أو ا<� ا( ر(/� ���ل ا�� ر -��4د $�(� -� ر ا���4اk*(����/� ان ا ds`...أو ا�إ (
1�8 ��وف ا��kd و� د2) �� ر J�)�$ �/ ي�K أي أن -� ر ). '&% 'lk ���ل ا�45(ا���`) '� ��وف ا(��ل� ��5 ��وف دا��-J ا� �K:� ا���4ا�/ )� . �� ر ا���4ا�- +q*� م�`:
��� ج ا��# ا("!�K�� /4 $�ة دا�ي :`�م ���c(��ل ات /� $&8 ا *� آ����5 /� �&�) /� ا� �Kي(:`�م -� ر ا�() . -� ر ا("!�a) /� أ_&Jd(ا���4ا�� :(�) أي أن -� ر. ا� �Kي
ج�K5(� إ)� �� � � :�4 �� ا��# ا(�,) و�)� �� آl ��# ا���4ا*� ��� !"� #�/��ل -� ر ��() �7 و/� 1 � '4م ا-, ل دا��ة ا� �Kي (. �/� ا(&� ا� �Kي ا�45 '&%
5� `� ��dkا ��� د &��# ا("!s)ا �����ا J*� ي :!*4م، و:!*4م�K �����1 /�ن -� ر ا� �� ر ا���4ا�� ذي ا`�(� ا*�- �� �- ا�45 ��� �/� وc�!�1 :�-�7 /�ق). أو ا* �� 46ا(ا!
ت آ��dة 46ا $4 -,) إ% ا�) ا(�����1(ا� �Kي :��� � آ��dة k) �� 4 اcيإ% �>� 8d�:آ( :���� ا`&8 . ا(��ل أو ا(� ورة J ا(��ل أو &�<� ا(�* �) �*J أو &(*4ة ا�� -���ي
�)�` � � �� ا�4:4ي &(��ل /� هbc ا�� �Jg�*- �� Jdd ا* �� 46ا &��# ا("!- )� ت:���� {c4:4 وآ�7 اd��& !ارة ا��ا �� �� -�� �� ا�� رات ا4وا��� وا�<&� '
��� .ا("!Jq1�� J�&)'
دا��ة ا� �Kي ����- '� _�� $,4–أ�! ء ا*() /� إ41ى �xآ ت ا��dول $ م أ41 ا(5!��94
�. (��ل -� ر أ�! ء /�,J 4ا��ة -�"�) و-�k+ �*`4ة �41 ا`�ا 7K ا!���� إ� �� ا{��) وآ و�) ����K b4: �/ ز���ق را -<�ج �� 56K Jd�: JK�� J� م �&.
��`� �� ا��� ا��4 &(���ت �7 ا`�ا 7 -- 6� )� و_��ه ؟ ( ذا :��% دا1 � ا��� _�� ا���k�: 4ن /�اغ ه�ا�% /% هbc ا(!�k: J`aن %/ JK� ��!: )� �: �& (� $
Ja`!ا bcل /% ه *�xاى :�4ث ا �)>� :*�ف �� J!' 7 -- ر ا4dء /% ا(��آ ت؟ه ��- (�&`� J�4>�� % ا�aق ا(
(�&`� J�4>�� ر ا4dء &(��آ ت ا�% -*() '&% �56د �"��b �� ا�aق ا(�- 1-soft starter
2- )�K J&���- د� /% ا(��آ ت ا�% -*() '&% 456 ����9
��ا% �`&�) ا�� ر ا(��ك و-�kن ��,&J �7 ا*�s ا4وار � ا�9<4ام �` و�J '!4 �4ء -�"�)�- ا! وآ+ ا�$�. :�4ث (��� /����'!4 -( س ا41 ا� �ار ا���� و�`�� /� ا*() � ذا-- 8
ا(��"�ق &�4ث ؟ و( ذا؟1 � �4ء ا�( س وذ} �ن) د$�`�50( -!��� 2�ل �� J�/ ي 41ثcر ا�a-!�`) �� ا �����ا
£: )� �)�&� ا% ا� �ار اgر دي ا%ا*d:�`- 5�)�$ �*g %ا �)�&� .ار-� ع ا� �ار ا) � ه� أه(�� -- 9Tertiary Winding(���ت؟ (ا �/
Tertiary Winding ال%/ ¦ /� إ% /% ا(���ت ه% �&� �g§ ا(��ل �
��<4م (�ور ��آ�d ا�� ر ا,��: ا(&� ت ا§��4ا��� و ا� �K:� و :��) '&% ه��� د� و:� ج 456 � ¦ &(��ل و :<�&� $�(� /� 1 � '4م إ-{ان ا�1( ل '&% ا(��ل و�K§ 4م>��:
��� و /� آ��� �� ا��1 ن -�kن $4ر-5 �&¦ $4رة ا`4رة '&% هcا ا(&� '� ا(&�����ا� ,ا(&� ت ا��2ى
ج ا`4رة و�k (�ور ��آ�d و /� أ�1 ن�K§ �&)ا اc,��:�أ�2ى � :�+ إ�9<4ام هر ا ا���`/.
�4ة ا<{ان ا���1 � /� ����ت ا`4رة ؟ -- 10 / � -- 1 (�&`- �:}& l�� �1 ا����a &�5اء ا(� . ا(-- 2 � 1 �/ ���� ( look out) ا!�sح -*�:# ا<{ان ا� ت ا��:� 3 --d&`�ا �� �:} � +k��4د.ا)�: � ء �1¦ ان ا{:�x �&`�:و ���
ت -- 11kdx (2-�4ث دا ��ا �������� ا� ��5kء ا a2ه� ا� ? ا!`) � .ز: دة ا�() -- 1 �x ��� ا� �ار او( دوا�� ا`,� -- 2d� س )- 4: 5 و��� ا(�!��) ($7a /� ا41 ا� �ار(ا4وا�� ا(����1 -- 3 س ��� ا� �ار وا�رض(ا* ز�� -- 4)-)
؟.ا�Kاع ����ت ا��ر:# -- 12 ا{6{اج ���ل 1 -- open delta ���ل أ�ــ -- 2
��<4م /� ����ت ا4� 2و1ا(���ت - 3 -- �� و-��<4م /� -�ر:# ا(�4ات.. ���ل ا(* و$� ا* ذا :��<4م-- 13) l�و J6او ��� م ا�qK ����5k`4رة اا ���q!� �/4؟؟6ال5او
مqK ا�9<4ام (s�: d9� J6او ��� :ب ا�-��ا�1 -- J6او ��� م ا�qK �/ ت `&� ا��ا/`� .$&� ا�k&�� ا�$�, د:� -- 24 �� -� ر -- 3�& �K �&���- ��K(�ود�k4ء ا�dا.
ه� و���� -���&� ال ـ-- 14� ?? Open delta ا�45 -�<4م /% ���ل
J641وث $,� ��� ا41 ا�و � ��9<4ا�� و ا�رض&�,�ل '&% 456 ا(�آ�d ا,��:� /% 1 /�� او ا�$ :� �� ز: دة� ر ا`,� /% ا�$ :� ا(�- b ا�� ر /ى��4:4 ا-�
�4ة ر�� ا<� ا�ا�7 -- 15 / ر '!4 ر�� ا(&� ت ��a:`�) ا�ر��(��� ؟(Y)ا()� � �K(�از4ة �6اء '4م ا� وذ} �(�:� ا�� رات ا{ا
16 -- ATS?? ه� � م :��<4م /� -�qK ����5ه�k`4رة ا4 ا�) ac( 8 رة /� ا"d' وه� J� (,�: ك د:{ل��� �' alternator �$ aل ا��: bي �4ورcوا ��k�K ا% آ����5k�)اac ة رات ا* د:� �7 ��ا'�� ��K -�آ��d '&% اk��� م q!ا اcز ه و:(�
زآ( :(� ac to dc وذ} ���:) matching ودا��ة rectifier و�6د دا��ة alternator %&' J-4ر`� lk' {(��ك وذ} /`� �(��د -�"�) اوذ ���&a)`4رة اج ا �Kإ
رات ا(�4ات ا* د:� /��� � -�-�7 $4رة ) د:!(�(ا� واcي :�a&8 ر/7 $4رة ا(��ك و� ج ا4:!(� '&%�K§ا وا® أ'&+.اcه
'4ة� ت أآ�� '� هcا ا(��gع ��6 ء ا(��&*� J:4 �� و +k��ت ا 1� �' �� >��)qK!�ع �� ا�ا اc��4 /� -�"�) ه>�� .ا(
ذا -- 17) �`d ر�6 او �ت :�4x 8ه �� ا"�ف ا<� k4 8�9 ا!' Armory ؟ �ت� k4 8�9 ا!' �`d ر�6 او و� :�+ 4xه �� 4x 8�: Armoryه �� ا"�ف ا< ا(��) او ا* زل
�) و�c} :`)ان -+ 4xه �� ا(��) �9ف :�k7 اa`� �1 � � &(��) و-`) �a�9ا + ()�-(� kا
�� ر و2��&Is.c �ت �� ا* زل /c5ا :£دي� k4 اx +- ان و$,� '(�isolating b ا� $&� ا�
18 --What is the IP standard "Protection degrees of enclosures :�kن ��kن �� ��ث ار$ م :� bc5 ا(*4ة �1¦وه� در�6 ا�( IP آ) 56 ز او �*4ة :�kن 5
ex. IP 543 dust �� وه� در�6 1( :� ا�5 ز" 5"ا�$+ ا�ول �K water or "liquid" وه� در�6 1( :� ا�5 ز ��" 4"ا�$+ ا�
mechanical impact وه� در�6 1( :� ا�5 ز ��" 3"ا� ¦ ا�$+�: �<�&�� k) ر$+ وه! ك در6 ت 1(
Kانو �g�: {8 وذ�k: � ¦ ن ا�$+ ا�K ر ان ا�1d�'ا� �/ c2 هbc ا( آ�!� ��``� mechanical impact
ذا -*�ف '� ال -- 19� ANSI DEVICE NUMBERS ؟ % � ت آ: رb '� ار$ م � ���d*- J'� ا�Kاع �<�&�J �� ا�(d' %ه:
NO.2 MEANS TIME DELAY NO.21 MEANS DISTANCE
NO.25 MEANS SYNCHRONISM-CHECK NO.27 MEANS UNDERVOLTAGE NO.30 MEANS ANNUNCIATOR
NO.32 MEANS DIRECTIONAL POWER NO.37 MEANS UNDERCURRENT OR UNDERPOWER
NO.38 MEANS BEARING NO.40 MEANS FIELD
NO.46 MEANS REVERSE-PHASE
NO.47 MEANS PHASE-SEQUENCE VOLTAGE NO.49 MEANS THERMAL
NO.50 MEANS INSTANTANEOUS OVERCURRENT NO.51 MEANS AC TIME OVER CURRENT
NO.59 MEANS OVER VOLTAGE NO.60 MEANS VOLTAGE BALANCE
MEANS PRESSURE (MECHANICAL PROTECTION) NO.63 NO.64 MEANS APPARATUS GROUND
NO.67 MEANS AC DIRECTIONAL OVER CURRENT NO.68 MEANS BLOCKING
NO.69 MEANS PERMISSIVE NO.74 MEANS ALARM
NO.76 MEANS DC OVER CURRENT NO.78 MEANS OUT-OF-STEP
NO.79 MEANS AC RECLOSING NO.81 MEANS FREQUENCY
NO.85 MEANS CARRIER OR PILOT-WIRE NO.86 MEANS LOCK OUT
NO.87 MEANS DIFFERENTIAL NO.94 MEANS TRIPPING
� ا����� ؟ � ه� 8d9 ار-� ع 9*� ا�,) /� -- 20s�>Kا $�ا 7 ا4ا��ة آ&(� ا����� $&� ا��ارةs�>Kا .ا��)4ة '!4 '(&�� ا�,) و�c} -�-�7 9*� ا�,( آ&(
ن ؟ ا�� ر ا(��دد او ا�� ر ا(��(�؟ ا:5( اآ�� �a2ا '&% -- 21�Kا� ��(� وذ} �JK �*&�م ان ا�� ر ا(��دد :(� 2�ل ا�� ر ا �k- 4$ن ا�6 �� �ول وه&�: ج)
�(� &���ر 2�ل ا,*`� ا ����5k�k؟ �a`!� J��d�6 ا,�� �(: ن ���K§ا %&' �a2(��دد أر ا ا�� ر ا(��(� ، هcا &��ددات ا(!<��s ا��
2000Hz �s�>!)رات ا 5-�3 ه��-{ أ60a2-50ا�� ر ا(��دد و:�kن -���� 30mAوا���)�� ف ا�� ر -���� ا�� ر ا(*gأ.
8 �!�!% 2 ص، و-,) أ'&% $�(� -� `�(� ا��دد وه� 1*d- (��ددر ا -<�&� �a2رة ا�� . ه��-{50 – 60�a>&رة '!4 ا��دد
ا�� ر ا(�-��d�*: 7 أ$) �a2ا �` رl�K 7� �K ا`�(� ا�� ر ا(��دد ذو ا��ددات ا(�-�*� وذو - ر&�� ر�- ��� ،�)�� �� ا�� ر ��1000&� أ���d '!4 -�دد ���40دد ا(K ه��-{ :*��d أآ�� أ�
�)�� �� ا�� ر ا(��دد 30ا(K :*�l�K �d ا�� ر ا(��(� أآ�� أ�)!�� ، ��d��13&� أ��&�� . ه��-{500أ���d '!4 -�دد
- �)�� ن '!4 $�+ �<�&�� و:<�&� '&% :<�&� أ�� ا�� ر ا(��دد '� أ�� ا�� ر ا(�K§ا +�6 1�8 ا��دد، /`�k: 4ن أ�� -� ر ذو b��أ s:أ K .$�(� -�دد ' � :!�,� '&% ا��وق أ�1
ن أو !`) در�6 -�Kº �� /�ق ا�45، �` و�� : ا<�aرة -*�4) '&% ��9 '�ا�4x (ة ا§� +� ر(ا���& �&kر ا � ر ا�� ر /� ا��+، وا{�� اcي 4xة ا�� ر، �Kع ا�� ر، ،(أو ا(��
�/ J *�ض�,*`� :�+ اا. ن ه� /� ا�� ر و�l /� ا����� -�K§ا %&' %)q*رة ا�a>ا. ��� ه� � ه�ة إ�2�ج ا`&8 �� - ��5k,*`� اب /� ا :�*�ض J ا(,� �a2أ
fibrillation �$�- � � م د$ ت ا`&8 و�q�Kاب إ�agه�ة إ �g ا4م أو g*� ، وه� ��dوأآ ،�s`&8 اا '&% ا�a2 (k�: �5/ {cدد، و��)ر ا ه�ة ه� ا��qا bc5� 8d��.
b وا41 أو ا(��دد ذو -�,) -�-�� �)�� ا��+ ����K (�ور ا�� ر ا(:� ا<�aرة '&% 2
d��: )� :� و� ��� ا<:��) ا§��kو��� /� ا< �2�ل ا �� �s�>!� 8-�ددات ��:���(� � ت ا(���:5 اK�:ف -�ز:7 ا���2�� 8d��) وا� � .ا
5 ��b4 ���ة �:&� و���¦ :(� �� ا����� -�ا«�!� ه� ا����� ا�� :��7�a ا�<� (J�2 ،J� *�ر�ا �k): � ر �-
ر ا���:� -�- Let Go Current b4!' يcر ا �J ه� ا���K �:��- ن �K§7 ا�a��: J��!� .وه� و/` &(!�!% ا(cآ�ر
ب ا����� -� ن، /�+ -�4:4 ا����� ا��!� -+ 1�K§ا +�ا«�!� �! ءا '&% أ$) 41 (` و�� 6�، أ� ا����� ا«�!� &�� ر ا(��(� /�5 65 ه��-{ �`�(� 50ا(��دد &�� ر�/ 110،��/
م ا� /� و¼56{ة /� ��وف '4م و�6د ر� ���، أ� إن و46ت ا� ��� /�ن ا�4هcا ¼6�، و&�45 ا(��(� 30ا«�� &�45 ا(��دد ه� �/ 60��/ .
- �/ gرة -*�(4 إ�a>ا ،J *�ض�ي :�+ اc{�� ار '&% ا وا(!�!% إ% $�(� ا�� ر و�Kع ا��l� &{�� ه�(��دد وا �)�� .�a2 و:<�&� � ��� ا�� ر ا(
- d�- �����رة ا�a2�/ �`/ ر�& ��- �5 ر ' ز�� ا��+ وا��وق ا!Kإ ����. 22 -- d�-�- ��-»رات ا ر-8 ا��:4' ,-
Ir �!`)ر ا ر ا�()IL - ا���- - Io.cر ر ا�,) Ioff - ز: دة ا���- - Is.c �,`ر ا �- -InL ()1� ر ا�- J� Ioff , InL,IL,Ir,Io.c,IS.C : ا�6 � ا�$ :� وا�( :� ؟؟� ه�ا��ق �� -- 23
�: م ��) K`�ل أ56{ة ا�$ :� �� ا��:� : ان ا�$q!6{ء �� ا l� ز -a&� '&% ان ا�5fire fitting
�: م ��) أ56{ة ا�( :�: ا� ا�(q!ز ه� 6{ء �� ا �� ز: دة ا�� ر -a&� '&% ان ا�5 ض وز: دة ا�45�>Kدة وا وز:
/� ا% ا��ق ��� ا�(gأ�: �: : وا�$�: 56 ز ا�$ (�� (a*& ��ر أ�و ( ا2�d&{( ا" ز:� 56 ز ا�$ :� :*() '!4 41وث ا«�
J�و:*() '&% ازا (a*4 41وث ا*� ()*: �: 56 ز ا�( ن ا�k4ر ا��/ �'��� ه� ا��ق ��� ا`��ز وا(�(( ت ؟ -- 24�
- ���k- ز���(�(+ : اا �k *� J}*-و (a*ا J,�>)ت ا ���k ا*a) و:,4ر أ�� &(5( ذ} ا*a) �*{ل) ا`�ا 7( ج ا%) ا� �Kى(ا���ز �-�� ج ا% �,4ر &�"c:� أ� ا(�+ -��: �:c"�& ر (�,4ر ����ت ا��
) ����ت ا�45 ا�-� ه�� وا(�(( ت ا"�� ا-� ه��؟ � ه� ا��ق ��� ا(�(( ت -- 25
Jه� ض -/`� ��) ��(+ 4g ز: دة ا�� ر ه% ا�% -*() � `�(�ا(�(( ت ا"��أ-��>Kدة وا ز: ��) ��(+ 4g ا���ب ا�رg% ا(�(( ت-ا�45 *� b ا�-� ه�� ه% ا�% -*() � `�(� وا�-�
س ا`4رةk*Kب-ا�� ا�� g&%-ا�رg% ا�-� ه% 4g ا� demand load ?و��� ال connected load ا��ق ��� ال -- 26
connect load �K ءة ه� ��(�ع ا�1( ل ا(��&J /% ا4ا��ة اJ���5k �9اء آgل '!4ك ا ��<4م او � ���
½� �Kوا �-��d)و-&��{:�ن وآ J ���<4م آ) دb /% و$� واl� 41 ال و-��k و��J6 و_� connect load J6 6 ت دى او اى 1 � ه� ��(�ع آ) ا�K&% ام ا q!8 ا�1 J&����
. ر4���9 demand load ا�
J /% و$� �*�� وه% ���ن ه� ا�() ا(a&�ب /%"x ن�k�� %&ت ا 6 و$� ��4د :*!% ا� رb '� الd' connect load %/ وب�s� factor ال J)9ا d:�`- diffarcity factor
J ن�k�� d _ b&�) '&% ا ودم وا��ا %/ %K � �9 س ان آ�/ ت '&% ا9 س ا�K ��<�&� �� و$
bت زرو .واو$ ت ا�5�9�ك ���kن /�5 ا$) /% او$27 -- J�d!64ول ا�4م ا>�� ذا -) recepticals bye 3 wire not 2wire as Egypt؟
زل ��!) � ��� �4 :�4ث �k�- hot and neutral onlyن ا���J ا�!!*/ short )5!����5 ء ا%kا ¾:��- +�: �gا�ر.
5�)&: ن ا�<� :*() آ�{ء �� ا4ا��ة و:`�م �4ور ا(` و�� و:(�/*!�4�Kر /� ا� ا��bر آ��� a2ة وا .و�� ا((�k ان :£دي هcا ا�� ر ا% ا�/
�kو %)�: �2¿ {&9 :(� ا�{ء ا�آshort �d /*!4 41وث ground ا��½ ا����� :�kن �5�� {&� ن ا%�ن �` و��J ا$) �ground `� �� ���k ا�� ر ��K� ن و� :(� ��Kو�� ا� ر �-
ن�Kا� %&' ��� - J l� 46ا ��"�. ا� �� ا�xح آ) �� ا�`�ات
: Recovery voltage: 7a$ 4*� 4ورة7 ا $ %&' �5q- ��ا �����ارة ه� ا��ا.
Resitriking voltage: ء 7 ا4ورة أ�!$ %&' �5q- ��ا �����ء ه� ا '(&�� إ � .�ارةا�
Transient over voltage: �/ ��q�&ت ا ' ا����� ا�� -�4ث /� ا��kd ه� ا�ر-�أ6{اء ا��kd أو /� 1 � 41وث -�� -���� '4ة '�ا�) ��) /,) أو -���) أي 6{ء ��
.ا,�ا'�First phase to clear the fault: 7 ه�a$ %&' 4ورة7 ا $ ��&� $)3Phase
short circuit) �(d$ 7a` 7 7 $� م ا41 ا� �ار �a$ ��&' ن�k: ¦�1 �:�2»ر:� ا�aا�,Kر:� ا«�2:� �(�ة و�aأ'&% �� ا ����/ d:�`- . ¦�1 ارة��ا J� À�a!- أي أن أول �ر
J� 7�-�-,�� و% ار إ أي اJK :�8 أن . �bc5 ا!`Resitriking voltage �a :,) ا�� .ا«�2:� :� أآ�� �� ا�aر1.5:��() /����
Symmetrical fault: ��� ل ا�� -�4ث '&% ا� �ار ا�a'ا وه� ا�cه �/ ���q!)وا1 � ا-{ان �/ ���q!)ا %`d- ل a'!�ع �� ا�ا.
bcن ه�k-و ل '&% �K'�� ه(a'ا�: 3phase fault
3phase to ground fault As Symmetrical fault: -�4ث '&% ا ��ل ا a'و-�4ث /� وه� ا� ��� ��5kا ���q!)
� 1 �' ���q!)ل -<�ج ا a'!�ع �� ا�ا اc41وث $,� '&% �ر وا41 أو �ر:� و/� ه� .ا�-{ان 1
ل '&% ���� أ�Kاع ه�a'ا� bcن ه�k-و: Single phase to ground fault Two phase to ground fault
Phase to phase fault Zero sequence impedance: �a>ر ا وه� $�(� ا(` و�� ا�� -*��ض ��ور -�
(Fault current If) �d' �a>ا �a`K �� ا�رض وه� (Fault) د إ% �a`K ا��(Neutral point) ���)ع ا�رض /� ا�K %&' .(ا�...... ,ر�&��, �<�:�(و-*�(5�)�$ 4
Source impedance وه� �k): ��45 وا�4ر ا,� �*K 5 ا(( K*� ا4ا2&�� �(�)�K أن�5q- ��ا �*K .'!4 41وث دا��ة $,� '&% �,4ر ا�45 وه� ا((
Inductive type voltage impedance: 414م ا>��أ�Kاع ����ت ا����� ا�� -ا!�ع �� ا(���ت '� �4dأ '() ا(��� �_�اض ا`� س وا�( :� و� :<�&� �4dأ '() هcا
و-*���� �d� 110V$�+ ا�45 ا* � إ% $�(� ��<4م �<��# $�(� ا�45 ��و-, ا�'�� د:��d�! ر c} -��� ��� ا�aر وا�رض ا�45 �` و�� ' �� 46ا ���&.
Out off phase switching: 7 ه� '4م -{ا�� '(&�� ا�,) وا����) � �ار $ 5!�� أي :�8 '&% ا` 7 -�() ��) هbc ا� � , ا� �ار أي و�6د /�ق ز�!� ���, ا4ورة /�(�d,: JKأي آ� Short circuit %&' 2phase ة�x d� 7 .و'&% �/� ا`
Over current ??ز: دة ا�� ر و Over load ا��ق ��� ز: دة ا�() --- 29 ز: دة ا�()
%��5kر ا �ت ���ة &�() '� ا`�(� ا(`!!J و -��(&5 ا(* ه% $�(� ا{: دة /% ا��� k4ة او ا .% 25ا% % 10-��اوح � ��� ز�!�� دون ان -�&� و
ل�� رة '� ���كd' %��51() آ K4!' ن �8 و �,(+ أذا آ آ��5% :`�م ���"�) ��9 !`) ا�`�' 4:}:� J�&' 8� 8 -� ر 1000 '&% ان :�kن وزن ا����آ�&��6ام و '!4 هcا ا�() :
�8 أ���d /�ذا �200`4ارة آ�&� �6ام /c5ا �*! b ان ا(��ك '&� ن 1200ا% زاد وزن ا�`8 -� ر آ%��5�� أ���d '� ا(,,+ '&�J و �c} 40ز: دة /�(`!: J�) هcا ا�() �9ف :
%&kر ا -��a2 46رةا{: دة /% ا�� ر '� ا`�(� ا(`!!J �9ف و ه! . أ��d,:240��d ا�� % �9ف :£دى هcا ا% -&� ا( دة ا* ز� ا�� :£دى ا% ار-� ع در�6 �1ارة� و . �ت و�
�: )1 7g�: {c ()�دة ا .&(��آ ت 4g ز: -,(+ ا��ت ا����5k ان -��() ز: دة /% ا�()d ���ة ز�!�� % 25 - 10-��اوح ��� _
.&(*4ة (*�/� ا�� ��) و :�8 ��ا6*� ا��آ� ا(,!*�. $,��ة دون ان -�&� رز: دة ا�� Over current
ا�� ر ا��5k% '� ا�� ر ا(`!� ا�% -£دى ا% إ-�ف ا(*4ة ا����5k دون ه% $�(� ا{: دة /%��2�-
�� �dن اآ�k- � d .�� $�(� ا�� ر ا(�!� % 50ز�!% و _����&� 5 -��() ز: دة -� ر -,(+K����5 اk(*4ات ار $,�( ا ان -�&� و(4ة ��ث ��اK% دون) -�
.:�8 ان -*() ا56{ة ا�$ :� $d) هcا ا{�� ا{:�% و ا(��غ �� ا�5اء ؟ � ا��ق ��� ا` 7 ا" زى و --- 30
�% ��� ا`�ا 7 ه� �Kع ا( دة ا* ز���ا(��<��4 /% إ � ء ا��ارة ا����5k ا�! ء ا��ق ا�7 `& ����� ./,) K`� ا���l ا�
Vacuum Circuit Breaker �� ا�5اءا` 7 ا(��غ - 1 �� ا�5اء �4ر�6 ' �� 46ا 46ا هcا ا!�ع �� ا`�ا �k- 7ن� _�/� أ � ء ا��ارة ���_� -(
-,) ا%1000000000 / 1 Torr ى��ا �"sا ��-
�K دا2&���� ()' �k): � {c !�ع وا اcب ه��' �� �d�*: اc7 و ه `& ����� ت ا����)& رات '&% هcا ا!�ع �� ا`�ا 7 و $� س ا(` و�� ا4ا2&�� � ا`�ا 7 و'!4 ا�6اء�d�2ا�
ت و و46 ان���)& �� 4:}: )� (� k 5 _�� 9&�(� :�+ ا4d�9ال _�/� أ � ء ا��ارة ��)�$�� k- %�1 �5د�4م /% ا>�� . آ�&� /��36ا,� �K و هcا ا!�ع : Oil Circuit Breaker ا` 7 ا{:�% - 2
-�kن _�/� أ � ء ا��ارة �(&£ة هcا ا!�ع �� ا$4م ا�Kاع ا`�ا 7 و � زال :��<4م �1% ا«ن و ت��� '4 '&% أ � ء ا��ارة ��� ا(� زل :' �:}� 8�: JKا �q1�� 8�: �k و �����ا�
رات دور:� &{:� �*4 '4ة '(&� ت /,)d�2{م ا� '() ا&`,� و :�+ -"��ة اذا 4م >���� و :'���� ان �1(� آ��d 46ا /% 1 � ا�9<4ا�� /% ا�45 /% ا��5د ا(!<��s و ا(���a9 و ��
% .ا* SF6 Circuit Breaker ا` 7 ا" زى - 3
ر /% ا�و�K ا���2ة +��Kا� %/ c2`�ا 7 ا!�ع �� اا اcآ���ة و ��*4دة و ه J �� �{ا: ت ا�5:��� .آ�&�/�� �1100د ا(<�&�� %�1 :��<4م /% 7�)6 �
�:�dkدس /&�ر:4 ا _�/� أ � ء آ��9 ' زل داSF6 (2 و /% هcا ا!�ع :��<4م _ ز 9 .ا��ارة
ت : 31a�)� �ت وا���9 ت ا�% :�8 -�ا/�ه�� ا(���ت وإدارات ا�$ :� ؟ � ه% ا
�� �ت ا��� :�8 أن -��ا/� ا1 - %��� % single line diagram�a�)&أو ا���4ا� ا�9+ ا�- 2 �: wiring diagram وا�� ر ا(��(� و-�ز:7 ا�� ر ا(�"�� ر9+ ا4وا�� ا� �K:� وا�$3 - �: �9) ا�$ رات 4--d�2وا� �K �9) ا,�5 - (�"�� � �� �9) ا�*&�( ت ا< ا�!�� ا�*&�( ت 6 -- 7 �: آ�وت أ56{ة ا�$5 دات ا��2 8 -x�K ر و��ا�� ا,�d :�ة ا*4ادات وأ56{ة ا`� س 9 -*� (�9
ر دوا�� ا���K�ك 10 -d�2�9) ا - 11 (�9 �a�)& ��!�ت ا K �dا 32 – ������ أو ا���4ا�� ت ا4وا�� ا�K�k� %ه ؟ � آ�� 1 -k� ا(� -�� وا ن - 2ds`ا ����ت ا�� ر- 3 ا�45 ����ت - 4���ا(���ت 5 -�� ا� '4ة -6� ا(���ت ا(
56 ز ا�$ :� ا�&�+ ؟ � ه% ا��وط – 33 %/ ا�ا86 -�ا/�ه- 1 ��9 � ر $,� أو -�دد :�8 أن :�kن 56 ز: ا��- ($�� bر�*x �64رس 46ا �1 �: ا�$
5�)�$ %a>�- 5 ا�5 ز أو _�� ذ} '!�4�&' �: ا`�(� ا(*- 2 ��� `�Kء:�8 أن :`�: ا� `�K � �: م ا�$qK م �kd�ا �� b��_ دون J}'`,� ون ا k� - 3 �'�� ن: اk� ف و'{ل م :�8 أن :�+ اآ��qK ن ��'� ا(a&��� وآ&( آ ا`,� �
ذ} -�aرت أ56{ة ا�$ :� �� ا(�1�ت ا�$ :� أآ�� �9'� آ&( آ ن ذ} أ/s) و'&% ��k�K إ% ا��9 -���k إ%k�5و��k$ ا�ا��)
در '&% ا*(): ا(���$�� 4 -$ �: م ا�$qK `� /% أن�وه% -*!% ا �`a!)ا %/ (a*ء ا أ�!��_ � !� %/ (a' ء و�6د ا(! � ا(���ل '!5 وأJK ا�% :�(�5 /`� و:�8 أ� :*() أ�!
J� '&% أداd&9 ��£: )� �: رات و/% ا�56{ة ا�4:�� :�46 � :�4ث أى 2&) /% 56 ز ا�$xإ إcKار '!4 و�6د 'a) دا5� %&2
��<4م ؟ � ا(`,�د : 34- �(���ت ا`� س و/�( ـ: ����ت ا`� س أو ����ت ا�56{ة -�() '&%
����ت ا�245 -����ت ا�� ر 1 - 89 أ56{ة و-��<4م هbc ا(���ت ���:) ا�� رات!� �s�>!� +�$ %46ا إ �� وا��5د ا*
س وا��k+ و'4اداتا�$ :� وا�` � $� ا�* � وا"�� /*aا . 5�$�� 8�إ% ا�56{ة ا�% -+ ذآ�ه وذ} �!�8 وهbc ا(���ت -`�م �!`) 1 � ا��kd و1
� آ( /% ����ت ا�� ر � 1�8 ا�� ر ا)`!� ¼56{ة و/% 5/ 400 أو(:��-400/ 1 � 8� 11000 أو 100 /11000أو 110/ 66000 أو 100 /����66000ت ا��k- 45ن ا!
/110��4>��1�8 ا�45 ا(`!� ¼56{ة ا( ��� . /�ا�4 ����ت ا`� س ؟ : 35�
م ا`4رة إ% $�+ �"��ة 1 -qK رات ��� أ56{ة ا`� س -��:) �56د و-�� �d9 -�kن �!�: وا��k+ وا(�ا$�d وأ56{ة ا�$
5 ذات -� ر و456دوا�� ا�56{ة '� ا4وا�� ا '{ل 2 -- �و�� !q+ ا`4رة وا�% -�kن �&� م ا�$ :� أو ا`� سqK ر 89 �45 و-�!� ��_ % '
c"- ��9ى �5 ا�56{ة /(�� :�kن ا�� ر ا� �Kى ا(`!� /% -�4�1 $�+ ا�� ر وا�45 3 -�$ +�`� أو �100ت ا�45 أ���d وا�45 ا� �Kى ا(`!� /% ���5أ���d أو ����1ت ا�� ر �/
110 ��/ 36 – ��)�& �d-ا�ا +�` ا(`,�د �� rated burden ؟
5 '&% ����ت ا�� ر أو ا�45 �,�� دا�(� '&% أن ه% ا`4رة&�)�- �k): %�ا ��dأ� ��� �(q- �$4ى ا���� 8�1 &(���ت $�(� ا<�a /% ا�� ر وزاو:� ا�J6 /% ا�4ود ا(�(�ح �5
37 – % �5 ا(`,�د � ��{ ا�p20 , 30 VA ؟ �1� %&' 8�k- �:�*�ا Name plate }��وا p ىc$+ ا�وا �: :*!% أJK ���ل -� ر &�$ ر�: %&' �5q: ف��ا p +$4$�5وه� رى ا���� %!*: Accuracy class ىc$+ ا�وا �) أ$,% 41ود اp �$4'&% :(�� ا��ف*� (�): ALF !*: ر وه� 20% أ�k): JK ��ور -� ر ا�ا-8��& �*g ن�k- أن �a:�x ��d ا<�a /% ا�4ود ا(`�رة 5K ء (��ل ا�� ر �7 �`
� أ�30��dا(��&� '&�J ا�1( ل�/ . ��&kا �a>ا �d�K %!*- أ�2ى �`:�a� (`!� و/% آ) ��20ور '!4 % 5أور ا �� ا���*g
%&' �&a: 30ا��1ال VA ا�d-ا�ا +�` ��)�& 8�k:5وP أو X 45�ر و/% ����ت ا 5 ر�{ 6pأو 3p'&% ���ل ا��`d�: CL أو KL
أو class 2أو class 0.5 و/% أ56{ة ا`� س -�kن class :*!% ا4$� أو ����ى ا�$45 20_�� ذ} �� ا`�+ وا��2ى `d�: n 8-ا�ر ا ت ا���' s� 4د' .
38 : � d�2ر ؟ه% ا� رات ا�ز�� &��آ4 �� ����1 ���ل ا�� س ا��9(�ار:� 1 -�$ �:�K ت ا��&)& )continuity( ر ا*{ل ��ا�a9 ا(��� 2 -d�2و�1000ا ��/ 7� �:�K و�� ا*{ل &(&� ت ا�`� (`-
�' %g*{ل10ا�رو�� ا أوم و� -`) �`��� �' %g7 ا�ر� ��� أوم ��20&(&� ت ا���4ا�
- 3 �a9ا�� ��da`ر ا d�2ر:� ا adا ��d ا���:) وذ} � ��ار -� ر �56 ا���4ا�% و$� س ا�� ر 4 -K ر d�2ى ا�K ا� ر ا��7d وذ} ���&�� 456 '&% ا(&� ا� �Kى و$� س $�(� ا�� ر 5 -d�2% ا�1% -,) إ
��d ��1&� ا��7d ا�% -4dأ �� ا!`�a ا�% إذا زاد ا�45 /�5!� /�ن -� ر ا(&� ا� �Kى % 10 �d� ن أى ز: دة �"��ة /% % 4:}:50 �!/ �a`!ا bcة 46ا و�*4 ه��dدة آ ا�45 -£دى إ% ز:
7d��(��ل ��1&� ا24) ا: {cر و� . /% ا��6- �k): �)�� س ا(` و�� ا4ا2&�� &(&� ا� �Kى وذ} '� �:� -���) �,4ر 456 ��$
�' J�/ +k��45ا�ر وا و�� ��"��ة و:�+ ر/7 ا�45 -4ر:�� و$� س $�+ ا��`� �:� �)��ا(�$� ا(` و�� * �Kن أوم �$ 8� ����9 $�(� ا�� ر ÷ ����9 $�(� ا�45= و-��8 ا(` و�� 1
س 1(�� ����ت ا�� ر ؟ – 39�$ �k): آ�� �� أ$�ب روز-� و:�+ -���) K , L أو S2 , S1 ا� �اف ا� �K:� (���ت ا�� ر :�+ /,)(���ت &�45 ا(��دد :(�k ا��k+ /% $�(�J إ% K`� ا����) ا(` �&� ¼ �اف ا� �K:� �,4ر
�È1 $�+ ا�� رKو K %�1,) إ% $�(� ا�� ر وا�% -"cى أ56{ة ا�$ :� و:�+ ر/7 ا�45 -4ر:��5 و:�+ ا�45 ا(! ��و:�+ -���) $�(� Inا�� ر ا�ا-�d (���ت ا�� ر
ب ا�(�� � ا�ا-8 &(��ل ا�� ر× ) '!4 ��ور ا�� ر ا�ا-8 ($�(� ا�45 ا(` س = 1J�&' �K(4ور وا و-` رن � `�(� ا�ا-�d �(�� ���ل ا��
ر ا(��(�؟– 40�� � �a�)ا �:c"- م qK ح�xا
ت ه%a�)ا %/ �)�� ر: ت ا�% �,4ر ا�� ر ا(ad% ا�ا ���أ56{ة ا �a9ا�� 5!�x +�: ر: ت -`�م ���4�1 ا�� ر ا(��ددadا %/ JKا�2{ا �k): �)�� و-��:&J إ% -� ر ��: _ %/ �)�� آ�� وا�� ر ا(k� `�ا 7 وا� �� ا�ه(�� إذ :��<4م /% دوا�� اk!��ول ا<
�)qKأ �:c"- %/:� وا و��م ا qKار وcK§ت وا� ءة ا��agار:� وأ��d �� ا�$ :� وا�-,g§ �1 ����� ا�ه(��x �� ر:� وأآ�� a� �� �9<4ام أآ�� ا�% :�8 -�/�� �, در �4:&� وذ} �
و�6د ا�� ر ا(��(� /% أ�9أ ا�qوف �1ارة ا{:� و���d در�6 �1ارة ا(&� ت ؟ � ه� ا��ق ��� ��d� ()' �:�qK در�6 - 41
ز �1ارة:*() ا�5 ز ا< ص �`� س در�6_ J� � خ �"(�ر /% ا{:��Kن �� ا�k�: وه� �ا{: �) -(4د آ��d وا" ز :,) ��*� J +k��:و ���dKأ �a9ا�� l�� خ إ% ا(£�x وK`� ا���Kا�
�`K �� ���'�)�� %/ ز ا§cKار 65ا���l ا{�d`�� و:(Jadg �k '&% در�6 �1ارة ا�5 ��K ذ} &�,) أو _��95وا�
�� إ� إنأ� ا� خ :���� �5 ز ا< ص �`� س در�6 �1ارة ا(&� ت /�5 ��) ا�5 ز ا��Kا� ر�- و�� :(� �5`� �� ��- /� إ% ا��ارة ا!g§ � � 89 �7 ا�� ر ا( ر ���ارة ا{:!�:
(��ل وهcا ا�� ر اcى :c2£ �� ���ل -� ر دا2) ا(��ل� ��و�c�k- {ن ا��ارة ا(£��ة �J�&'ت و �1ارة ا(&�)Kوإ ت ا�و% -�ds �1ارة ا{:� و41ه��� ت �� ا�'�)�� ����
%&'50��K در�6 و/% أ�Kاع 100 در�6 وا� �� &�,) 70cKºار در�6 ��"�) ا(�اوح وا� ت ��"�) ��(�'�% ا(�اوح وا§cKار وا�,) أ�2ى أر�*� ��(�' ت ����� ا�
؟؟) ا�$ :� ا! -�� �� -�&) ا" زات( ��2&{ '() 56 ز-�k/ �' +&kة – 42 رة '� و' ء �*K4% :���ى '&%d' �4!' �'�ا���� �� ا���!��م -a��ان '&% �a9 ا{:
� وآ):} � ء �(�&�K§ن ا�k: ن�k-و ��`d���l ز- �`K %/ +k��-ك �1ل ���ر و���- 5!� ) �1���� l��� ا*�ا�� $�&� K`� ا���l و:�آ8 هcا ا*�ا�� /�� / K`� ا�adذا ه�
���dKز '&% أ �J و-�آ8 ا�5�K (��لو��� ا % ا{:� ا�% -,) ��� 2{ان ا{:� ا���1 در�6 �7 ا�/`% �k: %�1ن ��ور ا{:� �� ا<{ان ا*&�ى إ% ا(��ل ��2) ا����dK �{او:�
2�ل �� �/ Jق و�� ء ��k+ ا§_K§ز ��2&{ وا 56 �a9وا41ة �� ا'&% -��� و-"&� ��ا �� م)� �� أو �*�k- 4:� ا{::} و-��<4م §�2اج ا" زات �*4 �¼ ا(��ل �
/�`�) وا�7g ا* دى)5�&' �"s- زات ن إ� /% 1 � K`� ا{:� أو و�6د _��/ ا*�ا�� ن 1&� ن إcKار و/,)�� ت '&% ا�� �7 وه(��� ا�
��dآ�� :(�k ا�,�ل –43K %&' ر ؟ d�2ر �4ون ا -��:) ����ت ا�45 و����ت ا���J أو �� ا*4اد ا(�آ�k): %' 8 ا�,�ل '&% �*&�� ت ���ل�K (��ل45 �� '&% ا�ا'&% ا(��ل أو '&% 2&�� ا`� س و:���ط أن -�kن هbc ا("cى أو �� ا��� ��� ا(�آ8
� ا* ا�56{ة ��ردة �7 ا&��1 أو� � �)�`� �� ��d ����ت ا�� ر إذا آ ن ا�K %&' 4اد�d�K ب�g (� ��d ����ت ا�� ر× ����ت ا�45 ����ب ��K
�k): ر �J أو �� ا����� أو و&�,�ل '&% �*&�� ت ����ت ا���K (��لا �� ا�,�ل '&�5��d ���� �� ا*4اد ا(�آ8 '&% ا<&�� أو ��K %&' ���d)ر ا ت ا�� ر أو 56 ز ز: دة ا��
�d�K %&' *4ادا �� � �)���ب �`�� �� ����ت ا�45 إذا آ ن ا�44 : (d$ ء ا�% :�8 ا��آ5!� 4�xه% ا� و7g ا�رg% ا(�&% ؟ � ف :�kن. ك 11-� ر 456 ا��آ4 �� /,) ا(5(� ا(�اد ا*() '&�5 و��k ����ت1 -
ا(�� ح ��,�ل و2 رج ا<&�� ل-���� '4م 2 -d`�9ا %g7 أرgو %/ �d_� 456 وذ} ����غ ا��5 ا("cاة � ر ا��آ4 �� '4م و�6د 456 3 -d�2ا� ,' �:� �' (� kا76 �� ا� ���d ا�45( �,' ) - 4 %g7 و�&� ا�رgو �K �% أو� �+ �� �56 ا(5(� ��� �� �56 ا�رg% ا�
ت : 45:c")� (`,�ده� ا 5 ؟ا��ازى وآ���� �*� (� ا�* ت ا�% -"cى �1 ت:c")رة -4ل '&% ا d' %ه �a�� %/ ازى��ز:7 و���&� '&% ا��ا
ن ا��ز:7 ds$ �� � ن ا��ز:7 و/% �1�1ا(���ت ��ds$ %&' 7:ز��ن 1ا ds$ %&' أو
ت /% �!�5% ا<�aرة �ن '!4 / وا�ا�� ���) �&��1 ا��ز:27 ,1ا��ز:7 :c")و-&} ا (, ت �� ا(��k: �aن ه! ك:c")ح �� أ41 -&} ا �) إذا + :�+ /,) ا(��kا76 '&% ا� � 456
7� (� �) أو ����ت ا�� ر إ� �*4 ا��آ4 �� '4م و�6د 456 ��1 ا��ز:7 و� :�+ ا�*kا ��آ4 �� ف ا��ازى /� :�8 ا*() '&% �24) ا4ا��ة إ� �*4 ا��. ك66و:!�da ذ} '&% دواا��2ى '� �:� ا��k+ و���q1 و�6د ا�45 '� �:� ���ل ا�45 /,) ا4ا��ة �� ا��5
. ف. ك 66ا4ا��ة أو ', ���d ا�45 وا< �� ��45 ا(��6د '!4 �24)46 : ()* ن ا��ز:7 456 �� ا(,�ح 5+ �ds$ %&'11 ف ؟. ك
�K ن (%94!5 ,�ds`ا {&- %&' ()* �K وه+ / :,�ح ��, ر ا�!��� �dوآ �����`� آ( نds`& 45�ا �:c"- در - : وا*() � :�+ إ� � ��وط ا� �� �d2 +5:4ة �(,
ن 1 -ds`& ىc")ا %��� �� ا����5 وإ�2اج '��� ا(�� ح 2 رج ا<&�� /,) ا(��ل ا� ت2 -:c"<�وج و�ت ا :c"� 7�)6 (,/ ت ا��2ى و���)ا �� ���رج ا 2 ��- إ�2اج ا(�
و'4م:� ا< ت ا��� إذا + :�+ ا��آ4 �� ا�,) �� ا�$��اب �� ا�{ء:c"� ازى أو��ت ا :c") %&��ا
ا��2ى ا��5 ( 2&�� ا`� س( إ�2اج '��� ����ت ا�45 2 رج ا<&�� 3 - ن 456 ا��آ4 4 -ds`<&��. ك ��11 /,) را�� ارج ا 2 J1 ��� 7gف وو ر و�6د 456 5 -d�2ر 456 ا d�2ا� ,' �a9ن ��ا ds`ف. ك11'&% ا ����� ا*() و-�kن أو% �a2ات ا����) و7g ارg% ��&% وه�a2 �2¿ bcة 6 - ر ا*{ل -"a% آ) 7 -d�2وا �/ q!ن �*4 ا ds`& �&��)ت ا ا���
رة �7g ا��"�) ؟ا(! و ف �*4. ك �11 :�J&)' 8 '!4 د�2ل 2&�� �2وج 456 – 47- 1 %&' J!� 7�$��ز:7 وا��ل ا���5 ء ا(! ورة �7 �K) إ����7 -*�ق اK4م و�6د أى ��ا' -
�) إن 2 -kع '&% رأس ا�g�)ا %gر/7 ا�ر J*/آ4 �� ر��و46 وا - 3 5 و-"��هK�{:��� وا ��- إذا {م ا��� ��ا6*� ����ى ا{:� /% ا(� ر '��� ا(�� ح �1%ا��آ4 �� '4م و 4-�� �"��ة �6د أى �*4ات 2&� أو /% �K و� آ- 5 �g�' ن�k- � %�1 �:}!d � 5�/ qK 4*� ��- ل �7 أى �xارة '4م د�2ل ا(�*�x� ا��آ4 �� '4م و�6د آ5!� '&% ا(�� ح أو أى �*4ات 6 - ن ا*() 7 -k� �' ل *�x� �&� إ�* د ا(�اد ا` :� وا��"�) ��) �� -��ا��آ4 �� -� 8-$�& �:c")ا �)�� ا�� ر ا(- 9 7gح /% و ر وا����) وا�,) ا��5k% -���) روز-� ا(��d�2ا�
��k�K �ى �, '8 د�2ل ا(�� ح /% ���ى ا�24ل ا�:(� 10 -k�)آ� ا��ا �q1�وا�:�� و� ح -�اJ6 ا�24ل وا�*��� ا,�����)&
$+ ا�رد:� و'!4 ا����) :�kن ��ا�a9'4م ا���xاك 11 -a *() إ�رد:� /% ا�ا l��ر §�6اءات*� ن ا����) و��k� �' ن �*�4ا�k: �2»رد:� ا�) و/�د ا����ا
ع ا��ز:7 '&12%a$ 7� ���-���) ا("cى �� إذا آ ن ا("cى :"cى ��1 ا��ز:7 :�+ ا�!��{ا�� �7 ا����) &��1 وذ} �2/ �� 41وث 'a)ا(��a أو� و�*4ه ا����) �� د�2ل ا
ا��� '� 8d9 ا�,) '&% �"cى �2وج �� ��1 ا��ز:7 /��,) ا("cى � (��a و:<�&�JK kو� - 13 ��&>& ��� :*� Jg����K ��4,& أى �a2 '!4 ا����) � :�8 أن :�kن ا�!% �)��� 9 48 – 4*� %��� ا,� �K ؟ � :�J&)' 8 '!4 -���( ���ل ر
5 ء أ�� ا�")1 -Kآ4 �� إ��ا أ/�اد ا,� �K ا��آ4 �� 2&� ا(�$7 �� آ) 2 - -�� ا(��ل �� ا����5 ا��آ4 �� '4م و�6د أى �5( ت '&% ا(��ل أو � ���:7 أو '&% 3-��
�a`K %&' (��6دة(��ل ار:# ا�- �!�k9 (���-دل و ا�*4 - �� (� ا("cى &(5( تا��آ4 �� -���) ا�� ر ا(- 5 (d$ 4آ��ح ا آ�� �� /,) 6(�7 أوJ6 ا(��k� -���) ا5 ء ا*() - 6�K � +k��& رة xل إ وا�,�ل '&% ا(�ا/`� '&% ا����) إر9 آ�� - 7k� ع -*&�( ت ا��k+ �����) اd-(��ل �� �56 اح ا ف . ك 66أو� :�7d ذ} ���
�56 �� ف. ك 11و�*4ه ن 456 را��/,) - 8ds`45 '&% . ك11ا�وى ا �ف �*4 ا��آ4 �� -�(�) ا(��ل و-
ا(���� ن 9 -ds`45 '&% ا�ا �dg 4!' È1�:1, 2JK� �k45 و�ات �"�� ا�a2 وى � � :�kن ��
ف وا("��:� �<�&��� /% '4د ا<�aات. ك 66ر�( ا4ا��-�� �<�&���� /% ا�45 �� �56 وا!�ع49 – :�8 '(&J '!4 -���) دا��ة �*4 ا,� �K ؟�
5 ء أ�� ا�") �� دا2) ا(��a أو �� 2 رج ا(��a � :�+ ا4dء /1% -Kأى '() إ� �*4 إ ا��k+ وإ��غ
ا4ا��ة و��ا/`�J '&% ا����) &��آ4 �� '4م و�6د 56 ت أ�2ى -*() '&% ا��آ4 �� -���) ا�� ر ا(��(� ا("cى &(5( ت 2 -- 3 %�!�k9 (���- +k��ت ا )�&*- 8� ن 1ds`<� واا ا��2ى أو� وإ��غ ا��k+ '!4 9`�ط أ41 :�+ ��ا6*� ا�45 إذا -+ ا����) �� ا��5 4 -
J6ا�و - 5 �*� ا���d� %&' 45 456 ا4ا��ة إذا �4ء ا��k+ ا����) �� -���) ��� ح ا4ا��ة و��{�56 �`� :�+ '() ا<�aات - 6�� إ�xاف �5!4س ا��k+ا�-
50 – �a�) ؟ � ه% 41ود '() /�د ا��"�) � دى وإذا ا4��9 /,) ����ت أو' 7g�ا ) ت ا��"�) )�&*� `d ()*ا +�: �� ك 66دوا
ا��"�) ا* دى ف -�kن -*&�( ت ا*() '� �:� ا��k+ و� :�8 -"��� و7g. ك 220ف أو . +k��ا �:� �' ���d)*() �1¦ أنا(,&�� ان ا�� ظ '&% ا��kd دون '&+ ا��k+ و� آ
����� ا��k+ و� :�+ /,) �k9!� ا<� :4و: إ� �*4 ا��آ4 ��� �a�)4م و�6د 456 �� ا' ح د�2ل ا4ا��ة و:(!7 د�2ل��� J6و�� /,) 6(�7 أو �&� ا���:7 را/* :4ك و:�s) ا(`
ا��ادث ذآ� ا�� ��) و'4م ا�"��� � دة �� �d2ة ا{��ء و'!4ا��وى /% أc2 ا`�ارات وا��9�8d9 (�&�- (5 ا� د�� و'4م: %�1 �`�`�& -�kاره
51 – %`- ��"�) وا,� �K ا�% ر�(� ��&� ت ا,"��ة &*d6ا�ه% ا � آ��dة ؟ �>� �� 1 - ��k��*() و1,� ارج ا ا�`�q ا� �� و-�ك آ) ا(� آ) 2)�/ ��s- � %�1 J� �&k-
�dأآ �&k�� {��! ت - 2:c")ل ا 4 ���q1 $�اءة أ1(*� �: ت �� أ56{ة ا�$��و'4د ��ات ا�,) ور/7 ا*
ت��' (`!- � %�1 س �( -8�k و�Kا1% -4و:!5��ت 2 �� &��ادث وا§1�&�- 5*d�: �):4$ $� �ن k) -"��� ا�1( ل أو در6 ت ا��ارة أو ���� ا�"��� /% $�+aأو '4ادات ا �ى ا{:
8�: 8d9 ح �4 �� ا�ر� ظ '&% ا(5( ت و-�`�� أ'&% '��& J�/�*� و����ى ا{:� و1(&J وو7g -�"�) ا(�واح ���q1 �1ارة ا(��ل - 3ا(5( ت و� ر/7 :4ك � ���:7 و� ا*() /% أآ�� �� � :�8 -�ك ��اد ���و�� � `�ب �� 4 -
1 ()'{��K و-*�ض ���- � %� �a>& و_��ك دى دون �2ف 5 -' ��_ bا�- )� �K �� ا�5�9{اء /��( إ��غ ر��l ا(��a أو ����ل ا,�
�1 ة أ�2} و-(!7 1 د�� آ��dة c`!- - 6 {� ع �!�g4م را76 آ) ا�و!- ��k (9 k�- و_��ك و� {��K �' ل���� ا(Kأ ) ر:� 7 -adا È1� 5�/ qKا$% و�4رع ار:� ه% ا adن ا� ���ا ��d(�&�ل وأ�ا �/ وآ�
�a�)& آ�� 8-k� ع ا(� -�� واg(�ا6*� أون �dت ا d) È1�
52 - �:��dا�� �*�/� �a2ط ا!`) ا�5ا��� اآ�d �� ا�*� ا����d:� /� ا<�aط ( ذا ا ا�ر��g؟ ع*x§ارى ا��ك (ا� ل ا��ارb �� ا§9`�KإJ�gت ا�ر�� kأ�9ع �� ا J�� /% ا<�aط ا�5ا
89 �7 ا(* �) ا��ارى!�- Jو� و�� ا(*�وف أن ا(` ه� ا" :� �� و�6د - 53� � ت ا�{:���q!� �/ �)���s<� -4ار �(��ك :*() '&% ا�� ر ا(
4K ا(*4ات� ت ا) ا(�4 وا(*4ات ا4وارة ا��2ى, ا��ر��� ( ا4وارة (a�� �/4��� ���؟ ��5kا
عa`K(*4ات �ن ا�ة اc5 وري 46ا�g ت >s)ة اcوب ان و�6د ��) ه ا(� �6ء &�� ر ا(�!%&' 5- ا�� ر ا(�! وب /� ا��"�) ا�'�� دي :£دي ا% -�$� �!���q ا�{:�� ا�� -*() ���آ
4K ��� ا�1 �( :£دي ا% 1,�ل ا�gار $4 -��4 ا(�� و�1% ا(��ر ا�K . ت /� ا(!���q وا��>s)!�ع �� اا اcو�6د ه �kو �q� ��k�- -24) ا*() �,�رة او-��
4K وا(��ر� ع ا�� ر ا(�! وب :�(� ا(a`Kاي -&� ا �� ����cا :�+ ا� آ�4 '&�5 .ا� .و/�,5 �,�رة دور:�
؟؟ Frequency load shedding ا�1( ل � ��دد � �*!% ر�� -- 54�'�$���� $� ا�() � ��دد 'k'
When the load increase ------------------the frequency decrease when the load decrease ------------------the frequency Increase
ت ا��دد /*!4 ز: دة ا�())k��� 7�a��- � ��dآ (k�� Frequency Governor #:�*- ن ا-�دد -`�م,`K م ا�� ظ '&%ا�(q!& %!� م %�1 :�q!ل ا�$) اه(�� /� ا ت ��,) ا�1(:
ا��9`�ار اي :(�k ا`�ل
��� ��5kل ا �4ر:� '!�4 :`) ا��دد ��8d ا{: دة :*!� هcا ا(,/ %&' �&a,) ا�1(�'&% ا���9 �� ا��:*� speed governor ا(� �6ة '&% ا�() و '4م $4رة 1 آ+ ا��دد
ن ا��دد ا(� À6 و :�+ /,)/ دة{:,`K ء او /� ا4dا:� و ان 9*d ��)`&�&� ا�هل ا ا�1( مq!ا �`���� و /`4 -�از�K ا�7g و + : ��5kا stability frailer %م ا q! � (,K !K /
�مqا � 1 l4ا�ا : How the voltage affect by Reactive Power??55
Answer: The voltage affects directly with the reactive power in the power systems so if the reactive power increased the voltage increase and vise versa when the reactive power
decrease the voltage decrease. ه� ا��ق ��� ا�ر�g وا!��-�ال ؟؟ -- 56� ا� ر:#
�� �� ا�56{ة او ا(*4اته� دا��ة 1( ��5kر ا ��ب ا��- �� �: ��� ��5kا ��� ب �,*`� آ��5,: � ر ��Kر '� ا� ر ا���� ���"- اذا و�) -� ر ا���ب وا"�ض �!5
�/ 5)�),- �/ �� 2 �`:� J #:ر��وا ��dا� �,K 41ود ��� ب آ��5a$و-�46 ا�ن ا
و�� ا�رض �:�+ _�59 /� ا�رض '!4 ����ى`� (*�: �' �5)3-{:4� اوم وذ} � �رض� J�_��-ر و ��ور ا��
ا!��-�ال ر ا�� ر و'�د-J ا% ا(,4ر و:�kن ا!��-�ال /�5�) ()k)وه� ا �)qKا�7 /� ا�ا {&� ا
-*�a 456:� واذا آ ن 4:} �,4ر ذو ار�*� ا9�ك و�5( آ ن b456 /� ا(, در ا��
456 ا�J6 و:*c63{�aر )/ ا<�(456 ا�&}=4 ا(��2ذ �� ا41 ا�9�ك وا!��-�ال / ن ا�5 آ( ان
�!*: ، J� (��)ز ا '() ا�5�� ج &<� �2 ا�ر�g � :��4 آ��5��K � 56 ز � (�"��()*��) �: . ا�5 ز ا�ر ، �gJ!k :��4 /`� /� -�/�� ا�(
- �/ ��9 ����2 ا�* دل J �5(� أ9 ��5kن. �"�) ا�56{ة ا �� :!a&� �� /�ذا آ ��5kر ا ا�� .ا�* دل �24) ا�5 ز /�5 :*�د '� �:� �`ld`� phase ld ا�aر
��1 ا�����K �� دل ا��ق ��� �2 ا�رg% و �2 ا�*!/�'. --57 ؟؟ load bank resistor ه� ال �
kا �$ a4 ا���4:} �,4ر ن ���ه� أK} اذا آ ��� او ��5{ $4رة ��5 آ�ن :�kن ��4ة آ��57a`!� ��_UPS %&' J-4ر$ �d�>- ك و-�:4 ان ا��(�) $d) ر�Ja '&% ا�() او ا JK�l ه!
� ��K ا�� &��� /�� هbc ا�kة ا� )���<4م ��(�'� ا(` و� ت ' �� ا`4رة وا(- ( LOAD BANK RESISTOR ) ���- ¦�1 {&5��ا1( � ه� �,((� '&�5 ��) ا�() و-
9 ل ا(�4ات ا�� -*() -��s ا� �6 ا% هbc ا(*4ات /�. ا9�� STANDBY �� ��� ����ت ا�45-- 58�� وا�� ر ؟؟ � ه� ا��ق ا�
�� � %�� �% ان ����ت ا�45 -,(+ &*() '&% /�# �"!�� % '&% 456 ا��ق ا�� و��� �
�% ��"��ا� ����ت ا�� ر -,(+ � % '&% ) ا�4:4(�4ا2) ا�kر &*() '&% /�# ��!� و�89 �7 -� ر ا�() !�: ��"�� 456.
'&% ا��آ4 �� و�6د ا�dدن وهcا �!5d!: ) ()�ر) ا .'&% ا�aف ا� �Kى (��ل ا���4ة و�6د �&� -- 59 / � governor ر��� ؟��ا (d$
ض ا��45 وذ} /� 1 � ز: دة ا�1( ل '&%�>K �a� under ا���4 :�4ث � :*�ف �voltage �'�9 ض �>K8 /� اd�: ض ا��دد n ا(�4 �(�>Kا �ا � � �� f اcي :`�م �
89 �د: �7 ا��دد ا*�$� ا� �� �9'� ا(�4!�- . دة -4/� و��9:} �&dدة /��� ا او �< ر air ا��"�) �9اء آ ن ه�اء (�از�K ذ} :�+ ز:
�)�� superheated steam *{مدة ا '&% ا��ر��� ��6ع torque �'�9 وذ} {: ض�>Kل و'4م ا .ا��دد ا��ر��� آ( آ ن و(�از�K ا�1(
Jq1�� ء ا��kd ا(�41ة ا�� '!�4 �:�+ ا&��ء �) ��k&� ز: دة ا�1( ل �bc5 ا�a:`� ا�ن �*4�Kا
ت -��4 ا�2ى + -�ز:*5 6{ء �!5 '&%:�46 ز: دة /� ا�1( ل :�a�� . ت ا���4ا�% (��ل ا�/7 �*4 أى - 60�&� �&���- (kx 8d9ه� ���- �a�kx %&' 4) د� ؟ �7!) zero sequence current 4 �� أن(�ا �� �- :£دى ��ا/`� ت ا!)� �kd�& J��:
.)ا!` ' �� /% �kdx ا!`) �( :!�� '!J أن -`) آ� ءة61 -- (�� ��� ا,�ا'� /�� 1 � آ( K*&+ ان � K*� ا,�ا'� -�(� �� ا��5د ا* �� ا��
�&+ 41و�5 -`�م ا( K*� ����:¾ ا�� رات ا* �� ا% �kdx ا��ر:#- {cو �g% ا�را � � و��� """" وا<��aة ا(*4ات �� ����ت و2�/J �� هbc ا��5د ا*
ا���:¾؟؟؟؟:*!� ��4 �� 41وث �+ -���) ا� ز �7 ا�ر �/ �g�Jqو�� ا�da*� أن : � :�8 ان -*() ا�,) اي أن ا56{ة ا�( :� �9ف -�bc5� l))-�ب((� ا�� رات ا* �� و�
رة ا�,) &` 7 ا`�:8 ��xم ���� ؟؟؟؟؟؟؟؟؟ و-`�م ����1) ا�kا bc`,� /5) ها �a`K JKم _�� ���� �1¦ ا�kا اcه�� � ����:¾ ا��!� اذا $� K*� ا,�ا'� �4وره و $�
`,� ا�رg% ا����5k إ% ا�رض � -*() أ56{ة� �� .ا�$ :� ا<����K �&�- �',�اا �*K آ���ة ان �K 5 *4د ��ات -��:¾ اآ�� �( ه% �,((� و ا�1g�*�
5 و JK % -�*a) '� أداء و� '&�J دون ان :�+ '() ��� � �: % -*() أ56{ة ا�$� 5 و ��� .ا�ر4g %g ا`,� �1¦ ان
J�: 5K %/ !`) و4ا:� �2 ا� %/ 5*g,�ا'� :�+ وا �*K � )4*� (d$ و �a�)ا �� J6�2و -24) '&% د�2 J�a�)& ا� �� و -*() � K*� ا,�ا'� '&% -��:¾ ا��!�� (d$ % ا�رضإ
5�: ا�56{ة ا(�اد 1(62 -- ��&a,� ه� BURDEN ؟؟ ���ل وه� ��d*: �&a '� 1() دوا�� ا`� س وا�$ :� ا(��&� '&% � �Kي BURDEN آ&(� ل BURDEN و -` س ال. ا�� ر� Volt Ampere 8 '&% ال�k- � )� Name ودا
Plate (�� +$15آ�VA 30اوVA ر$+ ال :cآ� ���اره� )���) Accuracyو دا5P20 �K � دا��ة $� س Cl 0.5 ة و$ :� او ���دا�� اذا آK اذا آ
%�1 /% 1 J '4م و�6د 1() '&% ا �ا/J ؟ ( ذا :��8 ا(��ل آ��5 ء-- 63 (��ل وآc} 6{ء ��� �� � ج وذ} ��6د 2�K4:4ي وا�`&8 اا �a!") 4م>��ا�� ر :
�� ا�زم *() ا(���� ��� ا4ا �&2J اي ان ا(��ل �:��ل آ) اa . ا��# ا("! ��5kا �$ 7�s: (� �6ر ��9 /� ( 6{ء �!5 آ(� $�4 /� ا�4:4 ا% ا(&� ت ا<�K 4�$ �� s:ك ا وه!
�� وا�{ء, ) 1 � ا�() � ج ا��# ا("!�K� 4م>�� ا��2 �� ا�� ر :� ا�1() ه� وا(� $�4 آ`4رة �1ار:� /� 1
$�4 ا5���ة ��8d ��ا�� ت ا -- 1������ �4�4 ا("!2 -- 4�$ ا�� رات ا4وا�� ��
/�� &(��ل !�'�� 1() ا(� $�4 آ(` و��k)ة ا��-��� '&% ا��ازي �7 ا(&� و:��{ /� ا4ا ا���4ا�� &(��ل
ر ا�("!� /� :�4 �1ارة /��- /�� &(��� آ(&� ا�k)ة ا��4:41 ا(��� و:��{ J /� ا4ا ا���4ا�� &(��ل ي �7 ا(&�:��� '&% ا��از
��5 ء؟؟ -- 64kف ا اذآ� ��ا1) اآ����5 ء :4dوkف ا ا�4:¦ و� :(�k اآ��K�,' �/ �)5� 46 ��dء أ� ��5kأن ا �&6
5 /� ا(�ا��ت . �� -���� اd!�� اcر:� وا�{:��� /�k)- �5. ا��9"! ء '!5�&' }k-�:و تd9 ��5 ء إ� ����2ا… ووا§��kو��K و وا«�ت وا�k+ :�5+ دور ان �K§أن ا ��_ . �k):و
��!,- ����5 ء إ% 2(kف ا ��ا1) اآ����5 ء: ا(�1&� ا�و% kا ���q1 ا�da*�� ا�� -�5q /� ه� ا�� اآ���� �:� �' أ�! ءه
�`' م ا< 9!�600/��ا� . ا�5اء و/� ا,� ه4ة c6ب ا�6�� ����� �� $d) ا(��د -(J�&' �& ي أcن ا ��5kون �ف ا��kن ا9+ إ��K K��ا
��K ��5 ء18ا`�ن : ا(�1&� ا�k4 ا�ت ���}�)- �d6�)ت ا آ!� و� آ�� ف ا��!�ا�� دو/� 9!� K��ا + �d �� �ف ا*� 1733وا
�� 9!: ا(�1&� ا�a�/ � a:§ا + `4 أدى هcا . �1800 �4أت � آ�� ف ا*(�د '&% :4 ا*��5 ء ا(���آ�k% درا�9 ا*(�د إا
آ�� ف ا���:# �� �ف ا* + ا§�K&�{ي /�داي 91831!� �4أت /�: ا(�1&� ا�ا�*� � ت ا,! '�� 4�20ا:� ا`�ن ��K '� هcا ا���:# /�`�da�ك ، �!�ب ، ( 6(�7 ا���…)
��� 5 ا* + ا§�K&�{ي : ا(�1&� ا<*d ���� !"��5kت ا آ��:) اcي أو�qK 46:� ا(�6� .. 1865 �1ا� 9!�
اcي $4 :�,) /� ا� �ت ا� ��؟ -- 65�: .وا�ر�g 41وث -��l ��� ا<� .12. 4: .41وث -��l ��� ا<� وا(�3. 4: .وا�ر�g 41وث -��l ��� ا(� $� أآ�� �� ا(��وض .4a& c2�� (�)�-.
�x 41وث"� ا�و% /� ا�d� ��_ أو �x d� (k�� �g<� وا�را ��� l��- " 7a`!- ء�Kء '� آ) أ ��5kا �����4 ELCB ا(!{ل ، ���K� *() ا` 7 ا�!' d ، و:�4ث ذ} _
��- ./� و7g ا��"�) -�kن ا(�
��K �x أو"/� ا� � ا�d� (k�� 4: x 41وث -��l ��� ا<� وا(�d� ��_� " �/ {cوآ����K ،(!{لا �� �����5 ء '� 6{ء �k7 اa`!- ،�*ا��ا � MCB *() ا` 7 ا�s:وأ ،
7gو �/ ��- �4 -�kن ا(�!' d .ا��"�) :�4ث ذ} _ �� �x أو _��"/� ا� � ا�d� (k�� �g4 وا�ر: �x 41وث -��l ��� ا(�d� " 7a`!-
ء ا(!�Kء '� آ) أ ��5kا����و41وث ذ} _�� ��-ELCB ، �d {ل ، ���K� *() ا` 7 ا� ��kن ا(� -�� /� و7g ا��"�) أم �، /� أ_&8 ا��1 ن
ا��ق ��� ال -- 66� electric field ,وال magnetic field؟ ت 9 آ!� أو آ!���� ��6د (electric field) ا��ق ه� ان!�x و�6د ����K ��!:
(magnetic field) 7� ��"�� ��}ا ال)!)��magnetic fieldت ����آ� أو ( !�� ����K ��!: electric field) ��"�� /% ا(��k ا�� ر ��`4م -- 67)!�� � '� ا�45؟ �J /% ا(&� ا�� ر �� �2 '� ا��
د��k:90ن ا�� ر /� ا(&� ����2 '� ا��� ب *)& ����K {در�6 وذ ر ا�� :�-� �!5�- �) ا��� /�ذا آ ن �* د� ا��� ه�k- �' رة d' ن�k-(&� وا
V=Vmcos(wt) � �&� ا��k� 4*� ر /��kن �* د� ا��
I(t)=imsin(wt) � :�kن ا�� ر ����2 ب � در90�6و�
� 1 �/ ا(�k�/ ��kن ا�� ر ه� -� g) ا�45 و-�kن �* د�J آ «-� أ�I(t)=-imsin(wt)
I(t)=imcos(wt+90) دا��b آJ���5 �7 ا*&+ ا�k: JKن ����ح اذا آ ن آ�� :(� ا�� ر /% ���k ���6د /%-- 68
1 � �,4ر ���دد؟ short ا(,4ر ا("cى �,4ر ���(� و:�kن %/ 1 � ا�� ر ا(��(� :`�م ا�� ر � :(� �� 2�ل ا(��k ��6د '{ل ��� ��1 �/ {cو ��k)ا
���� ��k)�5 كاq:ة و�� '!4 ا-( م (open circuit) J!�x ا4ا�� �): � s:ر ا 1 � ا�� ر ا(��دد /�ن ا�� �/ 2�ل ا(��k وlk*: �k ا-� هJ /� آ) ا���k)ت ��� �/� ا آ&( ��ت K,� دورة K,� دورة ���¦ -!�`) ا��!
ه� ا��ق ��� ���ل ا�� ر ا(��<4م /� ا`� س '� -- 69� ���� �/ J�4>��ت ا�� ر ا( ا�( :J ؟؟
ا`� س ه� $� س ا�� ر /� 1 �ت ا�() ا�da*� و���� ����ت ا�� ر ا< �� ��56{ة}56�� �� ل أ� ����ت ا�� ر ا<a'ل ا�� س ا�� ر 2�$ 5�����/ J: ا�(bc5 �a!")ن �!�!� ا�/ J�&'س -�(�{ �(!�!� و ا(���ت -*�(4 '&% و����5 /(���ت ا`�
4!' �d�K J� ' J$4� �a2 %!�!)ن '�وة ا�k-و b��",رات ا (KNEE POINT) bc5 ا�� ل ا(���ت �!<�Js أي :�4ثa'ا� � ع &`&8 ا�4:4ي bc5 ا(���ت /� 1dxا. ز�)�/ J: و �!�!� �a2 ��_ �!�!)� 4!' �a2 '!4 ا أ� ����ت ا�(�d�K b��",رات ا ��
�� bc5 ا(���ت ��-�*J أ:�JK � (KNEE POINT) و-�kن '�وة ا(!�!% ا�� رات ا* ع &`&8dxل :�4ث ا a'ا� � .ا�4:4ي bc5 ا(���ت /� 1
ذا :��<4م -- 70) fuse&CB %/ ؟ ��)' J: 1 ت ا��ز:7 او /% ا�(� �: )1 &�() وا(,4ر ا�( :J ه� '() 1( :Jا45ف ��
CB �6د ا6{اء�ا �qK {وذ 5&�/ � :J او� و/% 1)� 5 -`�م ال -`�م �� J�k�K k�� FUSE ك ز�� �*�� ��� '() ال 5 و-�,) ا4ا��b وه!&)*� FUSE &CB 4,`: � bوه�
J� ( PROTECTION COORDINATION)
ه� أ�Kاع ال -- 71� Faults �؟؟/� ا ��� ��5kت ا kd Fault In Electrical Power System:
1- Multi-phase Short Circuit "High Current will flow a- Balanced three phase Fault
b- Single Phase - to - ground Fault c- Double phase to ground Fault
d- Phase to phase Fault ه� Single Phase - to - ground Fault أ�5x أ�Kاع ا`,� ه�d:�`- J�41و �d�Kو
80 % ��� ل و :�kن /� ا<�aط ا�5اa'ت و �� ا� و:)�kأو ا ���-� �8d -&�ث ا*�ازل ��و آc} :�4ث '!�x 4خ أو آ�� أ41 ا*�ازل . ا`,� '!4 ز: دة ا� ��� أو K{ول ا(�a :�4ث
�K أوd)<� /�ق ا8 ��ور اd� ت ا(�-�*� -�� ا<���ور أو �!1 ا��`K �&- 8d��ت ا�ر��g :�4ث �d�k& �d�! . أو ��8d أ'( ل ا��� joints ا&� م �
2- Open Circuit/Phases "No current" 3- Contacts with Ground "Isolated system or High Impedance
grounded system
1 -- Why cables are not used for long distance transmission?
Cables are not used for long distance transmissions due to their large
charging currents.
2 -- Mention the 3 main parts of the cable?
Conductor, dielectric, sheath
3 -- What is the function of conductor?
Conductor provides the conducting path for the current.
4 - .What is the function of sheath in cables?
The sheath does not allow the moisture to enter and protects the cable
from all external influences like chemical or electrochemical attack, fire
etc.
5 -- Mention the conductor materials in cables?
Copper, Aluminium All occupies greater space than copper for a given conductance.
Both are high electrical conductivity.
6 -- What is the purpose of stranding of conductors?
Stranding increases the cable. It has flexibility. Resistance of the
7 -- Define the segmental conductors.
The stranded wires which are compacted by the rollers to minimize the air
spaces between the individual wires are called segmented conductors.
Here the conductor size is reduced for a given conductance.
8. State the properties of insulating materials.
It should have high insulation resistance, high dielectric strength, and
good mechanical properties, non-hygroscopic, capable of being operated
at high temperatures, low thermal resistance and low power factor.
9. Mention the commonly used power cables.
Impregnated paper, Polyvinyl chloride, polyethylene
10. Mention the advantages of PVC over paper insulated cables.
Reduced cost and weight, Insulation is resistant to water, Simplified
jointing, increased flexibility No plumbing required.
11. State the merits of paper insulated cables.
High current carrying capacity, long life and greater reliability
12. Where polythene cables are used?
-being non-hygroscopic used in cables for submarines and damp soil. - being lighter used as aerial cables for vertical installations.
13. State the advantages of polythene insulators.
They are non-hygroscopic, light in weight, low dielectric constant, low loss
factor and low thermal resistance.
14. By what materials cable sheaths are made?
Lead sheaths and Aluminums sheaths.
15. In what way Al sheaths are superior to lead sheaths?
Al sheaths are smaller in weight, high mechanical strength, greater
conducyivity, cheap, easy to manufacture and install, withstands the
required gas pressure without reinforcement.
16. Where CSA sheath is used in cables?
Corrugated seamless aluminums sheath is used in high voltage oil filled
cables and telephone lines.
17. Why it is used?
It is used because it is very flexible and easily by repeated bending the
sheath is not distorted and it is not damaged. It has lesser weight and
reduced thickness.
18. Why protective covering is done in cables?
To protect the cables from mechanical damage, corrosion and electrolytic
action when laid direct in the ground the protective covering is made.
19. By what material protective covering is made?
Bitumen &Bituminized materials, PVC and layers of fibrous materials.
20. What is meant by serving of a cable?
Layers of fibrous material permitted with waterproof compound applied to
the exterior of the cable is called serving of a cable.
21. Why armoring is done in the cables?
To protect the sheath from mechanical damage.
22. Why armoring is not done in single core cables?
The presence of magnetic material within the alternating magnetic field of
a single core cable produces excessive losses. Hence single core cables are
left unarmored with non-magnetic materials like tin-bronze or silicon-
bronze tapes or wires.
23. Why Al is used as an armour material?
It has non-magnetic properties, high conductivity and mechanical
strength.
24. What is meant by grading of cables?
The method of equalizing the stress in the dielectric of the cable is called
the grading of cables.
25.Mention the methods of cables. Capacitance grading and intersheath grading.
26.Why the capacitance of the cable is very high than the capacitance of the overhead lines?
The distance between the conductors are small. The distance between the cores and the earthed sheath is also small. The permittivity of the cable insulation is 3 to 5 times greater than
that of air insulation. 27.Write the expression of the capacitance of a single core
cable.
( (2πε) ----------- = C=q/v
( ln(R/r)
28.What is meant by charging current of a cable? The capacitance of a cable determines the charging current. The charging current restricts the use of cables on EHV lines. The current carrying capacity of an a.c cable is also reduced by the
charging current.
29.Why power loss occurs in the dielectric of a cable? -due to conductivity of insulation
-Dielectric hysteresis or dielectric absorption. -Ionization or corona
30. Why all transmission and distribution systems are 3 phase systems?
A 3 phase a.c circuit using the same size conductors as the single phase circuit can carry three times the power which can be carried by a 1 phase circuit and uses 3 conductors for the 2 phases and one conductor for the neutral. Thus a 3 phase circuit is more economical than a 1 phase circuit in terms of
initial cost as well as the losses. Therefore all transmission and distribution systems are 3 phase systems.
31. Why the transmission systems are mostly overhead systems?
Because of the cost consideration, the transmission systems are mostly overhead systems.
32.Why all overhead lines use ACSR conductors? ACSR conductors comprises of hard drawn aluminium wires
stranded around a core of single or multiple strand galvanized steel wire. They provides the necessary conductivity while the steel provides the necessary mechanical strength. Has less corona loss. The breaking load is high and has less weight. 33.Why transmission lines are 3 phase 3 wire circuits while
distribution lines are 3 phase 4 wire circuits? A Balanced 3 phase circuit does not require the neutral
conductor, as the instantaneous sum of the 3 line currents are zero. Therefore the transmission lines and feeders are 3 phase 3
wire circuits. The distributors are 3 phase 4 wire circuits because a neutral wire is necessary to supply the 1 phase loads
of domestic and commercial consumers. 34.Why overhead line conductors are invariably stranded? They are stranded to make them flexible during erection and
while in service.
35 . Stat the advantages of interconnected systems. Any area fed from one generating station during overload hours
can be fed from another power station and thus reserved capacity required is reduced, reliability of supply is increased
and efficiency is increased.
36. What is a ring distributor? A ring distributor is a distributor which is arranged to form a
closed circuit and is fed at one or more than one point. 37. State any two advantages of ring main system.
Less voltage fluctuations at consumer’s terminals.Less copper is required as each part of the ring carries less current than in
radial system. 38. Mention the disadvantages of a 3 wire system
In 3 wire system a third wire is required.The safety is partially reduced.A balancer is required and therefore cost is increased. 39. What are the advantages of a 3 wire dc distribution system
over a 2 wire dc distribution system? If 3 wire system is used to transmit the same amount of power
over the same distance with same efficiency with same consumer voltage we require 0.3125 times copper as required in
2 wire system.
40. Mention the differences between 3 wire and 3 phase 4 wire distribution system?
3 phase 3 wire is employed for balanced loads, but 3 phase 4 wire is employed for unbalanced loads.
3 phase 3 wire is used for transmission but 3 phase 4 wire is used for distribution of power to consumers.
41. State kelvin’s law. The annual expenditure on the variable part of the transmission system should be equal to the annual cost of energy wasted in
the conductor used in that system. 42. State any two limitations of kelvin’s law.
It is difficult to estimate accurately the annual charge on the capital outlay. It does not give the exact economical size of the
conductor. 43. Define resistance of the transmission line.
It is defined as the loop resistance per unit length of the line in a single phase system. In 3 phase system it is defined as the
resistance per phase. 44. Define inductance of a line.
It is defined as the loop inductance per unit length of the line.Its unit is henrys per meter.
45. Define capacitance of a line. It is defined as shunt capacitance between the two wires per
unit line length. Its unit is farads per meter. 46. What is skin effect?
The steady current when flowing through the conductor ,does not distribute uniformly, rather it has the tendency to concentrate near the surface of the conductor. This
phenomenon is called skin effect. 47. Why skin effect is absent in dc system?
The steady current when flowing through a conductor distributes itself uniformly over the whole cross section of the
conductor.That is why skin effect is absent in dc system. 48. What is the effect of skin effect on the resistance of the line?
Due to skin effect the effective area of cross section of the conductor through which current flow is reduced. Hence the resistance of the line is increased when ac current is flowing.
49. On what factors the skin effect depend? Nature of the material, Diameter of the wire , Frequency and
shape of the wire.
50. Define symmetrical spacing. In 3 phase system when the line conductors are equidistant
from each other then it is called symmetrical spacing. 51. What is the necessity for a double circuit line?
To reduce the inductance per phase and to increase the efficiency.
52. Mention the factors governing the inductance of a line. Radius of the conductor and the spacing between the
conductors. 53. Define a neutral plane.
It is a plane where electric field intensity and potential is zero. 54. Define proximity effect.
The alternating magnetic flux in a conductor caused by the current flowing in a neighbouring conductor gives rise to a circulating current which cause an apparent increase in the resistance of the conductor.This phenomenon is called as
proximity effect.
55. What is the effect of proximity effect? It results in the non uniform distribution of current in the cross
section, and the increase of resistance. 56. What is a composite conductor?
A conductor which operates at high voltages and composed of 2 or more subconductors and run electrically in parallel are called
composite conductors. 57. What is a bundle conductor?
It is a conductor made up of 2 or more sub conductors and is used as one phase conductors.
58. Mention the advantages of using bundled conductors. Reduced reactance, reduced voltage gradient , reduced corona
loss .reduced interference 59. What is corona?
The phenomenon of violet glow, hissing noise and production of ozone gas in an overhead line is called corona.
60. Mention the factors affecting corona. Atmosphere,conductor size, spacing between conductors and
line voltage. 61.Define critical disruptive voltage.
It is defined as the minimum phase voltage at which corona
occrus. 62. Define visual critical voltage.
It is the minimum phase voltage at which corona appears all along the line conductors.
63. State any two merits of corona. Reduces the effects of transients produced by surges.System
performance is improved. 64. Give the two demerits of corona.
The transmission efficiency is affected. Corrosion occurs. 65. Mention the methods of reducing corona effect.
By increasing the conductor size and conductor spacing.
. Why ACSR conductors are used in lines? If the size of the conductor is larger corona effects are reduced and reduces the proximity effect.Hence they are used in lines.
67. Define medium lines. Lines having length between 60 and 150 km and line voltages
between 20 and 100kv are called medium lines. 68.Define short lines.
Lines having lengths below 60km and voltages below 20kv are called short lines.
69.Mention the limitations of end condenser method. This over estimates the effects of line capacitance.It is assumed
to be lumped or concentrated. 70. Mention the demerits of HVDC transmission.
Electric power cannot be generated at high dc voltages. The dc voltages cannot be stepped up for transmission of power
at high voltages. The dc switches and circuit breakers have their own limitations.
71. What are the advantages of high voltage ac transmission. The power can be generated at high voltages.
The maintenance of ac substation is easy and cheaper. 72. Mention the disadvantages of high voltage ac transmission.
An ac line requires more copper than a dc line. The construction of an ac line is more complicated than a dc
transmission line. Due to skin effect in the ac system the effective resistance of the
line is increased. 73. Mention the limitations of using very high transmission
voltage. The increased cost of insulating the conductor.
The increased cost of transformers ,switch gears and other
terminal apparatus. 74. Mention the terminal equipments necessary in HVDC
system. Converters, mercury arc valves and thyristors.
75. Define sag of a line. The difference in level between the points of supports and the
lowest point of the conductor is called as sag.
76. Mention the factors that affect sag in the transmission line. Weight of the conductor,length of the span , working tensile
strength and the temperature. 77. What is the reason for the sag in the transmission line? While erecting the line , if the conductors are stretched too much between supports then there prevails an excessive
tension on the line which may break the conductor. In order to have safe tension in the conductor a sag in the line is allowed.
78. Mention the methods of laying the cables. Direct laying , draw in system and solid system
79. Mention the advantages of direct laying of cables. It is simple and cheaper method.It gives the best conditions for
dissipating the heat generated in the cables. 80. State any 2 disadvantages of direct laying method.
Localisation of fault is difficult . It cannot be used in congested areas where excavation is inconvenient.
1. What are the functions of protective relays
To detect the fault and initiate the operation of the circuit breaker to isolate
the defective element from the rest of the system, thereby protecting the system from
damages consequent to the fault. 2. Give the consequences of short circuit.
Whenever a short-circuit occurs, the current flowing through the coil increases to an
enormous value. If protective relays are present , a heavy current also flows through the
relay coil, causing it to operate by closing its contacts.The trip circuit is then closed , the
circuit breaker opens and the fault is isolated from the rest of the system. Also, a low
voltage may be created which may damage systems connected to the supply.
3. Define protected zone. Are those which are directly protected by a protective system
such as relays, fuses or switchgears.If a fault occurring in a zone can be
immediately detected and or isolated by a protection scheme dedicated to that particular
zone. 4. What are unit system and non unit system?
A unit protective system is one in which only faults occurring within its
protected zone are isolated.Faults occurring elsewhere in the system have no influence
on the operation of a unit system.A non unit system is a protective system which is
activated even when the faults are external to its protected zone. 5. What is primary protection?
Is the protection in which the fault occurring in a line will be cleared by its
own relay and circuit breaker.It serves as the first line of defence.
6. What is back up protection?
Is the second line of defence , which operates if the primary protection
fails to activate within a definite time delay. 7. Name the different kinds of over current relays.
Induction type non-directional over current relay,Induction type directional
over current relay & current differential relay. 8. Define energizing quantity.
It refers to the current or voltage which is used to activate the relay into operation.
9. Define operating time of a relay. It is defined as the time period extendind from the occurrence of
the fault through the relay detecting the fault to the operation of the
relay. 10. Define resetting time of a relay.
It is defined as the time taken by the relay from the instant of isolating
the fault to the moment when the fault is removed and the relay can be reset.
11. What are over and under current relays? Overcurrent relays are those that operate when the current in a
line exceeds a predetermined value. (eg: Induction type non-
directional/directional overcurrent relay, differential overcurrent relay)whereas undercurrent relays are
those which operate whenever the current in a circuit/line drops below a
predetermined value.(eg: differential over-voltage relay)
12. Mention any two applications of differential relay. Protection of generator & generator transformer unit; protection
of large motors and busbars .
13. What is biased differential bus zone reduction? The biased beam relay is designed to respond to the differential
current in terms of its fractional relation to the current flowing through the
protected zone. It is essentially an over-current balanced beam relay type with an additional
restraining coil. The restraining coil produces a bias force in the opposite direction
to the operating force.
14. What is the need of relay coordination? The operation of a relay should be fast and selective, ie, it
should isolate the fault in the shortest possible time causing minimum disturbance to
the system. Also, if a relay fails to operate, there should be sufficiently quick backup
protection so that the rest of the system is protected. By coordinating relays, faults can always
be isolated quickly without serious disturbance to the rest of the system.
15. Mention the short comings of Merz Price scheme of protection applied to a power transformer.
In a power transformer, currents in the primary and secondary are to be compared.
As these two currents are usually different, the use of identical transformers will give
differential current, and operate the relay under no-load condition. Also, there is usually a
phase difference between the primary and secondary currents of three phase transformers.
Even CT’s of proper turn-ratio are used, the differential current may flow through the
relay under normal condition. 16. What are the various faults to which a turbo alternator is
likely to be subjected? Failure of steam supply; failure of speed; overcurrent; over
voltage; unbalanced loading; stator winding fault .
17. What is an under frequency relay? An under frequency relay is one which operates when the
frequency of the system (usually an alternator or transformer) falls below a certain value. 18. Define the term pilot with reference to power line protection. Pilot wires refers to the wires that connect the CT’s placed at the
ends of a power transmission line as part of its protection scheme. The
resistance of the pilot wires is usually less than 500 ohms.
19. Mention any two disadvantage of carrier current scheme for transmission line only.
The program time (ie, the time taken by the carrier to reach the other end-upto
.1% mile); the response time of band pass filter; capacitance phase-shift of the
transmission line . 20. What are the features of directional relay?
High speed operation; high sensitivity; ability to operate at low voltages; adequate
short-time thermal ratio; burden must not be excessive. 21. What are the causes of over speed and how alternators are
protected from it? Sudden loss of all or major part of the load causes over-
speeding in alternators. Modern alternators are provided with mechanical centrifugal
devices mounted on their driving shafts to trip the main valve of the prime mover when a
dangerous over-speed occurs.
22. What are the main types of stator winding faults? Fault between phase and ground; fault between phases and
inter-turn fault involving turns of the same phase winding.
23. Give the limitations of Merz Price protection. Since neutral earthing resistances are often used to protect
circuit from earth-fault currents, it becomes impossible to protect the whole of a star-
connected alternator. If an earth-fault occurs near the neutral point, the voltage may be
insufficient to operate the relay. Also it is extremely difficult to find two identical CT’s. In
addition to this, there always an inherent phase difference between the primary and
the secondary quantities and a possibility of current through the relay even when there is
no fault. 24. What are the uses of Buchholz’s relay?
Bucholz relay is used to give an alarm in case of incipient( slow-developing)
faults in the transformer and to connect the transformer from the supply in the event of
severe internal faults. It is usually used in oil immersion transformers with a rating over
750KVA. 25. What are the types of graded used in line of radial relay
feeder? Definite time relay and inverse-definite time relay.
26. What are the various faults that would affect an alternator? (a) Stator faults
1, Phase to phase faults 2, Phase to earth faults
3, Inter turn faults (b)
1, Earth faults 2, Fault between turns
3, Loss of excitation due to fuel failure (c) 1, Over speed 2, Loss of drive
3, Vacuum failure resulting in condenser pressure rise, resulting in
shattering of the turbine low pressure casing (d) 1, Fault on lines 2, Fault on busbars
27. Why neutral resistor is added between neutral and earth of an alternator?
In order to limit the flow of current through neutral and earth a resistor is
introduced between them. 28. What is the backup protection available for an alternator?
Overcurrent and earth fault protection is the backup protections. 29. What are faults associated with an alternator?
(a) External fault or through fault (b) Internal fault
1, Short circuit in transformer winding and connection 2, Incipient or slow developing faults
30. What are the main safety devices available with transformer? Oil level guage, sudden pressure delay, oil temperature
indicator, winding temperature indicator .
31. What are the limitations of Buchholz relay? (a) Only fault below the oil level are detected.
(b) Mercury switch setting should be very accurate, otherwise even for
vibration, there can be a false operation. (c) The relay is of slow operating type, which is unsatisfactory. 32. What are the problems arising in differential protection in
power transformer and how are they overcome? 1. Difference in lengths of pilot wires on either sides of the relay.
This is overcome by connecting adjustable resistors to pilot wires to
get equipotential points on the pilot wires.
2. Difference in CT ratio error difference at high values of short
circuit currents that makes the relay to operate even for external or through
faults. This is overcome by introducing bias coil.
3. Tap changing alters the ratio of voltage and currents between HV and LV sides
and the relay will sense this and act. Bias coil will solve this. 4. Magnetizing inrush current appears wherever a transformer is
energized on its primary side producing harmonics. No current will be seen by
the secondary. CT’s as there is no load in the circuit. This difference in current
will actuate the differential relay. A harmonic restraining unit is added to the
relay which will block it when the transformer is energized.
33. What is REF relay? It is restricted earth fault relay. When the fault occurs very near
to the neutral point of the transformer, the voltage available to drive the earth
circuit is very small, which may not be sufficient to activate the relay, unless the
relay is set for a very low current. Hence the zone of protection in the winding of the
transformer is restricted to cover only around 85%. Hence the relay is called REF relay.
34. What is over fluxing protection in transformer? If the turns ratio of the transformer is more than 1:1, there will
be higher core loss and the capability of the transformer to withstand this is limited
to a few minutes only. This phenomenon is called over fluxing. 35. Why busbar protection is needed?
(a) Fault level at busbar is high (b) The stability of the system is affected by the faults in the bus
zone. (c) A fault in the bus bar causes interruption of supply to a large
portion of the system network.
36. What are the merits of carrier current protection? Fast operation, auto re-closing possible, easy discrimination of
simultaneous faults .
37. What are the errors in CT?
(a) Ratio error Percentage ratio error = [(Nominal ratio – Actual ratio)/Actual
ratio] x 100 The value of transformation ratio is not equal to the turns ratio.
(b) Phase angle error: Phase angle _ =180/_[(ImCos _-I1Sin _)/nIs]
38. What is field suppression? When a fault occurs in an alternator winding even though the
generator circuit breaker is tripped, the fault continues to fed because EMF is
induced in the generator itself. Hence the field circuit breaker is opened and stored
energy in the field winding is discharged through another resistor. This method is known as
field suppression. 39. What are the causes of bus zone faults?
_ Failure of support insulator resulting in earth fault _ Flashover across support insulator during over voltage
_ Heavily polluted insulator causing flashover _ Earthquake, mechanical damage etc.
40. What are the problems in bus zone differential protection? _ Large number of circuits, different current levels for different
circuits for external faults.
_ Saturation of CT cores due to dc component and ac component in short
circuit currents. The saturation introduces ratio error. _ Sectionalizing of the bus makes circuit complicated.
_ Setting of relays need a change with large load changes. 41. What is static relay?
It is a relay in which measurement or comparison of electrical quantities is made
in a static network which is designed to give an output signal when a threshold condition
is passed which operates a tripping device. 42. What is power swing?
During switching of lines or wrong synchronization surges of real and reactive
power flowing in transmission line causes severe oscillations in the voltage and current
vectors. It is represented by curves originating in load regions and traveling towards relay
characteristics. 43. What is a programmable relay?
A static relay may have one or more programmable units such as microprocessors
or microcomputers in its circuit. 44. What is CPMC?
It is combined protection, monitoring and control system incorporated in the static
system. 45. What are the advantages of static relay over electromagnetic
relay? o Low power consumption as low as 1mW
o No moving contacts; hence associated problems of arcing, contact bounce,
erosion, replacement of contacts o No gravity effect on operation of static relays. Hence can be
used in vessels ie, ships, aircrafts etc.
o A single relay can perform several functions like over current, under
voltage, single phasing protection by incorporating respective functional
blocks. This is not possible in electromagnetic relays o Static relay is compact
o Superior operating characteristics and accuracy o Static relay can think , programmable operation is possible
with static relay
o Effect of vibration is nil, hence can be used in earthquake-prone areas
o Simplified testing and servicing. Can convert even non-electrical
quantities to electrical in conjunction with transducers. 46. What is resistance switching?
It is the method of connecting a resistance in parallel with the contact space(arc).
The resistance reduces the restriking voltage frequency and it diverts part of the arc
current. It assists the circuit breaker in interrupting the magnetizing current and capacity
current. 47. What do you mean by current chopping?
When interrupting low inductive currents such as magnetizing currents of the
transformer, shunt reactor, the rapid deionization of the contact space and blast effect
may cause the current to be interrupted before the natural current zero. This phenomenon
of interruption of the current before its natural zero is called current chopping.
48. What are the methods of capacitive switching? • Opening of single capacitor bank
• Closing of one capacitor bank against another 49. What is an arc?
Arc is a phenomenon occurring when the two contacts of a circuit breaker
separate under heavy load or fault or short circuit condition. 50. Give the two methods of arc interruption?
_ High resistance interruption:-the arc resistance is increased by elongating, and
splitting the arc so that the arc is fully extinguished _ Current zero method:-The arc is interrupted at current zero
position that occurs100 times a second in case of 50Hz power system
frequency in ac. 51. What is restriking voltage?
It is the transient voltage appearing across the breaker contacts at the instant of arc being extinguished.
52. What is meant by recovery voltage? The power frequency rms voltage appearing across the breaker
contacts after the arc is extinguished and transient oscillations die out is called
recovery voltage. 53. What is RRRV?
It is the rate of rise of restriking voltage, expressed in volts per microsecond. It is
closely associated with natural frequency of oscillation. 54. What is circuit breaker?
It is a piece of equipment used to break a circuit automatically under fault
conditions. It breaks a circuit either manually or by remote control under normal
conditions and under fault conditions. 55. Write the classification of circuit breakers based on the
medium used for arc extinction? _ Air break circuit breaker
_ Oil circuit breaker _ Minimum oil circuit breaker
_ Air blast circuit breaker
_ SF6 circuit breaker _ Vacuum circuit breaker
56. What is the main problem of the circuit breaker? When the contacts of the breaker are separated, an arc is struck
between them. This arc delays the current interruption process and also
generates enormous heat which may cause damage to the system or to the breaker itself. This is
the main problem. 57. What are demerits of MOCB?
_ Short contact life _ Frequent maintenance _ Possibility of explosion
_ Larger arcing time for small currents _ Prone to restricts
58. What are the advantages of oil as arc quenching medium? • It absorbs the arc energy to decompose the oil into gases,
which have excellent cooling properties
• It acts as an insulator and permits smaller clearance between line conductors
and earthed components 59. What are the hazards imposed by oil when it is used as an
arc quenching medium? There is a risk of fire since it is inflammable. It may form an
explosive mixture with arc. So oil is preferred as an arc quenching medium.
60. What are the advantages of MOCB over a bulk oil circuit breaker?
• It requires lesser quantity of oil • It requires smaller space
• There is a reduced risk of fire • Maintenance problem are reduced
61. What are the disadvantages of MOCB over a bulk oil circuit breaker?
o The degree of carbonization is increased due to smaller quantity of oil
o There is difficulty of removing the gases from the contact space in time
o The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization.
62. What are the types of air blast circuit breaker? _ Arial-blast type
_ Cross blast _ Radial-blast
63. What are the advantages of air blast circuit breaker over oil circuit breaker?
o The risk of fire is diminished o The arcing time is very small due to rapid buildup of dielectric
strength between contacts
o The arcing products are completely removed by the blast whereas oil
deteriorates with successive operations 64. What are the demerits of using oil as an arc quenching
medium? • The air has relatively inferior arc quenching properties
• The air blast circuit breakers are very sensitive to variations in the rate of rise
of restriking voltage • Maintenance is required for the compression plant which
supplies the air blast 65. What is meant by electro negativity of SF6 gas?
SF6 has high affinity for electrons. When a free electron comes and collides with
a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative
ion is formed. This is called as electro negativity of SF6 gas. 66. What are the characteristic of SF6 gas?
It has good dielectric strength and excellent arc quenching property. It is inert,
non-toxic, noninflammable and heavy. At atmospheric pressure, its dielectric strength is
2.5 times that of air. At three times atmospheric pressure, its dielectric strength is equal to
that of the transformer oil. 67. Write the classifications of test conducted on circuit
breakers. _ Type test
_ Routine test _ Reliability test
_ Commissioning test 68. What are the indirect methods of circuit breaker testing?
o Unit test o Synthetic test
o Substitution testing o Compensation testing
o Capacitance testing 69. What are the advantages of synthetic testing methods? • The breaker can be tested for desired transient recovery
voltage and RRRV. • Both test current and test voltage can be independently varied.
This gives flexibility to the test
• The method is simple • With this method a breaker capacity (MVA) of five time of that
of the capacity of the test plant can be tested.
70. How does the over voltage surge affect the power system? The over voltage of the power system leads to insulation
breakdown of the equipments. It causes the line insulation to flash over and may
also damage the nearby transformer, generators and the other equipment connected to
the line. 71. What is pick up value?
It is the minimum current in the relay coil at which the relay starts to operate.
72. Define target. It is the indicator used for showing the operation of the relay.
73. Define reach. It is the distance upto which the relay will cover for protection.
74. Define blocking. It means preventing the relay from tripping due to its own
characteristics or due to additional relays. 75. Define a over current relay.
Relay which operates when the current ia a line exceeds a predetermined value.
76. Define an under current relay? Relays which operates whenever the current in a circuit drops
below a predetermined value.
77. Mention any 2 applications of differential relays. Protection of generator and generator-transformer unit:
protection of large motors and bus bars
78.Mention the various tests carried out in a circuit breaker at HV labs.
Short circuit tests, Synthetic tests& direct tests. 78. Mention the advantages of field tests.
The circuit breaker is tested under actual conditions like those that occur in the
network. Special occasions like breaking of charging currents of long
lines ,very short line faults ,interruption of small inductive currents etc… can be
tested by direct testing only.
79. State the disadvantages of field tests. The circuit breaker can be tested at only a given rated voltage
and network capacity.
The necessity to interrupt the normal services and to test only at light load
conditions. Extra inconvenience and expenses in installation of controlling
and measuring equipment in the field.
80. Define composite testing of a circuit breaker. In this method the breaker is first tested for its rated breaking
capacity at a reduced voltage and afterwards for rated voltage at a low
current.This method does not give a proper estimate of the breaker performance.
81. State the various types of earthing. Solid earthing, resistance earthing , reactance earthing , voltage
transformer earthing and zig-zag transformer earthing.
82. What are arcing grounds? The presence of inductive and capacitive currents in the
isolated neutral system leads to formation of arcs called as arcing grounds.
83. What is arc suppression coil? A method of reactance grounding used to suppress the arc due
to arcing grounds.
84. State the significance of single line to ground fault. In single line to ground fault all the sequence networks are
connected in series. All the sequence currents are equal and the fault
current magnitude is three times its sequence currents.
85. What are symmetrical components? It is a mathematical tool to resolve unbalanced components into
balanced components.
86. State the three sequence components. Positive sequence components, negative sequence components
and zero sequence components.
87. Define positive sequence component. -has 3 vectors equal in magnitude and displaced from each
other by an angle 120 degrees and having the phase sequence as original vectors.
88. Define zero sequence component. They has 3 vectors having equal magnitudes and displaced from
each other by an angle zero degees.
89. State the significance of double line fault. It has no zero sequence component and the positive and
negative sequence networks are connected in parallel.
90. Define negative sequence component. It has 3 vectors equal in magnitude and displaced from each
other by an angle 120 degrees and has the phase sequence in opposite to its
original phasors. 91. State the different types of faults.
Symmetrical faults and unsymmetrical faults and open conductor faults.
92. State the various types of unsymmetrical faults. Line to ground ,line to line and double line to ground faults 93. Mention the withstanding current in our human body.
9mA 94. State the different types of circuit breakers.
Air ,oil,vacuum circuit breakers. 95. Define per unit value.
It is defined as the ratio of actual value to its base value. 96. Mention the inductance value of the peterson’s coil.
L=1/3wc2 97. Define single line diagram.
Representation of various power system components in a single line is
defined as single line diagram. 98. Differentiate between a fuse and a circuit breaker.
Fuse is a low current interrupting device. It is a copper or an aluminium wire.Circuit breaker is a high current interrupting
device and it act as a switch
under normal operating conditions. 99. How direct tests are conducted in circuit breakers?
Using a short circuit generator as the source. Using the power utility system or network as the source.
100. What is dielectric test of a circuit breaker? It consists of overvoltage withstand test of power frequency
lightning and impulse voltages.Testa are done for both internal and external insulation
with switch in both open and closed conditions.