Directional under-power protection function block description

Document ID: PRELIMINARY VERSION

Budapest, October 2009

Directional under-power protection function block description

Document ID: PRELIMINARY VERSION

Budapest, October 2009

Directional under-power protection function

PRELIMINARY VERSION 2/9

User’s manual version information

Version Date Modification Compiled by

Preliminary 24.11.2009. Preliminary version, without technical information Petri

Directional under-power protection function

PRELIMINARY VERSION 3/9

CONTENTS

1 Directional under-power protection function ........................................................................4

1.1 Application ....................................................................................................................4

1.2 Mode of operation ........................................................................................................4

1.3 Structure of the directional under-power protection algorithm .....................................5 1.3.1 P-Q calculation ......................................................................................................5 1.3.2 Directional decision ...............................................................................................6 1.3.3 The decision logic ...............................................................................................7

1.4 Technical summary ......................................................................................................8 1.4.1 Technical data .......................................................................................................8 1.4.2 Summary of the parameters .................................................................................8 1.4.3 Summary of the generated output signals ............................................................9 1.4.4 Summary of the input signals................................................................................9 1.4.5 The function block .................................................................................................9

Directional under-power protection function

PRELIMINARY VERSION 4/9

1 Directional under-power protection function

1.1 Application The directional under-power protection function can be applied mainly to protect generators (or any other elements of the electric power system) if the active and/or reactive power has to be limited in respect of the allowed minimum power.

1.2 Mode of operation The inputs of the function are the Fourier basic harmonic components of the three phase currents and those of the three phase voltages. Based on the measured voltages and currents, the block calculates the three-phase active

and reactive power (point S in Figure 1-1) and compares the P-Q coordinates with the

defined characteristics on the power plane. The characteristic is defined as a line laying on the point SS and perpendicular to the direction of SS. (The SS point is defined by the “Start power” magnitude and the “Direction angle”.) The under-power function operates if the angle of the S-SS vector related to the directional line is above 90 degrees or below -90 degrees. At operation, the “Start power” value is increased by a hysteresis value.

Figure 1-1 The directional under-power decision

Q

P

Direction angle

Start power

SS

S

S-SS

α

Q

P

Start power

operate

Directional under-power protection function

PRELIMINARY VERSION 5/9

1.3 Structure of the directional under-power protection algorithm

Fig.1-2 shows the structure of the directional under-power protection (DUP32) algorithm.

Figure 1-2 Structure of the directional under-power protection algorithm The inputs are

the RMS value of the fundamental Fourier component of the three phase currents (IL1, IL2, IL3),

the RMS value of the fundamental Fourier component of the three phase voltages (UL1, UL2, UL3),

parameters,

status signals. The function can be enabled or disabled. The status signal of the VTS (voltage transformer supervision) function can also disable the directional operation. The outputs are

the binary output status signals. The software modules of the directional under-power protection function:

1.3.1 P-Q calculation

Based on the RMS values of the fundamental Fourier component of the three phase currents and of the three phase voltages, this module calculates the three-phase active and reactive power values. The input signals are the RMS values of the fundamental Fourier components of the three phase currents and three phase voltages and the three line-to-line voltages. The internal output signals are the calculated three-phase active and reactive power values.

Q

P

RCA

start only

&

&

1 OR BLK

VTS

START

TRIP t

P

Q

UL1

UL2

UL3

IL1

IL2

IL3

start

Start power

1 parameters

DUP 32

Directional under-power protection function

PRELIMINARY VERSION 6/9

1.3.2 Directional decision

This module decides if, on the power plane, the calculated complex power is closer to the origin than the corresponding point of the characteristic line. The operation of this function is

explained in Figure 1-1.

The internal input signals are the calculated active and reactive power values. The internal output signal is the start signal of the function. Integer parameter

Parameter name Title Unit Min Max Step Default

Direction angle (See Figure 1-1)

DUP32_RCA_IPar_ Direction angle deg -179 180 1 0

Table 1-1 Integer parameter of the directional decision

Float parameter

Parameter name Title Unit Min Max Digits Default

Minimum power setting (See Figure 1-1)

DUP32_StPow_FPar_ Start power % 1 200 -1 10

Table 1-2 Float parameter of the directional decision

Directional under-power protection function

PRELIMINARY VERSION 7/9

1.3.3 The decision logic

This part of the function block combines status signals to make a decision to start. Additionally to the directional decision, the function may not be blocked by the general “Block” signal, and may not be blocked by the signal “Block for VTS” of the voltage transformer supervision function. If the parameter setting also requires a trip signal (DUP32_StOnly_BPar_=0), then the measurement of the definite time delay is started. The expiry of this timer results in a trip command. Enumerated parameter

Parameter name Title Selection range Default

Switching on/off of the function

DUP32_Oper_EPar_ Operation Off,On On

Table 1-3 The enumerated parameter of the decision logic

Boolean parameter

Parameter name Title Default

Selection: start signal only or both start signal and trip command

DUP32_StOnly_BPar_ Start signal only 0

Table 1-4 The Boolean parameter of the decision logic

Timer parameters

Parameter name Title Unit Min Max Step Default

Definite time delay of the trip command

DUP32_Delay_TPar_ Time delay msec 0 60000 1 100

Table 1-5 Timer parameter of the decision logic

The input status signals of the OC function block:

Binary status signal Title Explanation

DUP32_VTS_GrO_ Block from VTS Blocking signal from the voltage transformer supervision function

DUP32_Blk_GrO_ Block General blocking signal

Table 1-6 The binary input status signals of the decision logic

The output status signals of the OC function block:

Binary status signal Title Explanation

DUP32_GenSt_GrI_ General Start General start signal of the function

DUP32_GenTr_GrI_ General Trip Trip command of the function

Table 1-7 The binary output status signals of the decision logic

Directional under-power protection function

PRELIMINARY VERSION 8/9

1.4 Technical summary

1.4.1 Technical data

Function Effective range* Accuracy*

*To be defined by types tests

Table 1-8 Technical data of the directional under-power protection function

1.4.2 Summary of the parameters Enumerated parameter

Parameter name Title Selection range Default

Switching on/off of the function

DUP32_Oper_EPar_ Operation Off,On On

Table 1-9 The enumerated parameter of the directional under-power protection function

Boolean parameter

Parameter name Title Default

Selection: start signal only or both start signal and trip command

DUP32_StOnly_BPar_ Start signal only 0

Table 1-10 The Boolean parameter of the directional under-power protection function

Integer parameter

Parameter name Title Unit Min Max Step Default

Direction angle (See Figure 1-1)

DUP32_RCA_IPar_ Direction Angle deg -179 180 1 0

Table 1-11 Integer parameter of the directional under-power protection function

Float parameter

Parameter name Title Unit Min Max Digits Default

Minimum power setting (See Figure 1-1)

DUP32_StPow_FPar_ Start power % 1 200 -1 10

Table 1-12 Float parameter of the directional under-power protection function

Timer parameters

Parameter name Title Unit Min Max Step Default

Definite time delay of the trip command

DUP32_Delay_TPar_ Time delay msec 0 60000 1 100

Table 1-13 Timer parameter of the directional under-power protection function

Directional under-power protection function

PRELIMINARY VERSION 9/9

1.4.3 Summary of the generated output signals

Binary status signal Title Explanation

DUP32_GenSt_GrI_ General Start General start signal of the function

DUP32_GenTr_GrI_ General Trip Trip command of the function

Table 1-14 The binary output status signals of the directional under-power protection function

1.4.4 Summary of the input signals Binary status signals The directional under-power protection function has binary input status signals. The conditions are defined by the user, applying the graphic equation editor.

Binary status signal Title Explanation

DUP32_VTS_GrO_ Block from VTS Blocking signal from the voltage transformer supervision function

DUP32_Blk_GrO_ Block General blocking signal

Table 1-15 The binary input status signals of the directional under-power protection function

1.4.5 The function block

The function block of the directional under-power protection function is shown in Figure 1-3. This block shows all binary input and output status signals that are applicable in the graphic equation editor.

Figure 1-3 The function block of the directional under-power protection function

The names of the input and output signals are explained in Table 1-14 and Table 1-15 above.