Generator Relay Model: LHVRT

 

To be documented.

Treatment of Model in Power Flow Contingency Analysis

When a transient stability model is used in the power flow contingency analysis using the special option for the power flow contingency solution, then the model determines how to report violation for the Monitor Only option as well as specifying a TimeDelay and Trip/Act action. The following table describes this and uses the following text conventions.

Model Evaluation

Description

Specific Implementation for this model

Monitor Only

Determine a Boolean result to indicate whether the stability model is “violated” and ready to do something?

Find the highest low voltage value specified (for all dvtrpX values which are negative these are the vref+dvtrpX values) which has a time-delay associated with it which is less than the TSModelMaxDelay specified as part of dynamic model input data (call this UseLowVolt). For the value found for UseLowVolt, take the corresponding Voltage Trip Time (dttrpX values) and call this UseLowVoltTime.

 

Find the lowest high voltage value specified (for all dvtrpX values which are positive these are the vref+dvtrpX values) which has a time-delay associated with it which is less than the TSModelMaxDelay specified as part of dynamic model input data (call this UseHighVolt). For the value found for UseHighVolt, take the corresponding Voltage Trip Time (dttrpX values) and call this UseHighVoltTime.

 

Evaluate whether

“Present Voltage PU > UseHighVolt” or

“Present Voltage PU < UseLowVolt”

TimeDelay used in Trip/Act

Time in seconds that the model needs to remain “violated” before it will actually apply an action.

If Violated because of exceeding UseHighVolt, then TimeDelay is UseHighVoltTime

If Violated because of exceeding UseLowVolt, then TimeDelay is UseLowVoltTime

Trip/Act Action

If violated for the particular time, then this procedure must be written to actually implement the action.

Model will open the generator

 

Model Equations and/or Block Diagrams

The values of dvtrp1, dvtrp2, … dvtrp10 represent deviations from the value of Vref. The test for determining whether the relay will trip is as follows.

Value = Monitored Voltage in pu – Vref

If (dvtrp1 > 0) and (Value > dvtrp1) then activate timer for dttrp1 else Reset the timer

If (dvtrp1 < 0) and (Value < dvtrp1) then activate timer for dttrp1 else Reset the timer

 

Each timer acts independently of other timers. If a time remains active for longer than the respective dttrpX value, then it will trip the generator.

As an example, if the low voltage trip levels are at 0.70, 0.45 and 0.15 and the high voltage trip levels are at 1.10 and 1.23 then both of the following would result in the same behavior (although specifying Vref as 1.0 seems the easier choice)

 

As an example, if the low voltage trip levels are at 0.70, 0.45 and 0.15 and the high voltage trip levels are at 1.10 and 1.23 then both of the following would result in the same behavior (although specifying Vref as 1.0 seems the easier choice)

Vref dvtrp1 dvtrp2 dvtrp3 dvtrp4 dvtrp5
1.0 -0.30 -0.55 -0.85 0.10 0.23
1.05 -0.35 -0.60 -0.90 0.05 0.18

Parameters:

Vref Voltage ref., Hz
dvtrp1 Delta voltage trip level, pu
dvtrp2 Delta voltage trip level, pu
dvtrp3 Delta voltage trip level, pu
dvtrp4 Delta voltage trip level, pu
dvtrp5 Delta voltage trip level, pu
dvtrp6 Delta voltage trip level, pu
dvtrp7 Delta voltage trip level, pu
dvtrp8 Delta voltage trip level, pu
dvtrp9 Delta voltage trip level, pu
dvtrp10 Delta voltage trip level, pu
dttrp1 Voltage trip time, sec.
dttrp2 Voltage trip time, sec.
dttrp3 Voltage trip time, sec.
dttrp4 Voltage trip time, sec.
dttrp5 Voltage trip time, sec.
dttrp6 Voltage trip time, sec.
dttrp7 Voltage trip time, sec.
dttrp8 Voltage trip time, sec.
dttrp9 Voltage trip time, sec.
dttrp10 Voltage trip time, sec.
Alarm If greater than zero, no tripping action is enforced; a message is printed when a trip level is exceeded.

Model supported by PSLF