Woodward MFR300-71M/K42 8444-1104

Woodward  MFR300-71M/K42 8444-1104

Phase Shift

General notes

A vector/phase shift is defined as the sudden variation of the voltage curve which may be

caused by a major source load change.

The unit measures the duration of a cycle, where a new measurement is started with

each voltage passing through zero. The measured cycle duration will be compared with

an internal quartz-calibrated reference time to determine the cycle duration difference of

the voltage signal.

A vector/phase shift as shown in ╚═▷ Fig. 38 causes a premature or delayed zero passage.

The determined cycle duration difference corresponds with the occurring phase shift

angle.

The monitoring may be carried out three-phase or one/three-phase. The monitoring can

be configured in different ways. The vector/phase shift monitor can also be used as an

additional method to decouple from the grid. Vector/phase shift monitoring is only

enabled after the monitored voltage exceeds 50% of the PT secondary rated voltage

Voltage is monitored depending on parameter “Monitoring” (param

eter 8806 Ä p. 64). This function allows the monitoring of the

voltage quality over a longer time period. It is realized as a 10

minute moving average. The function is only active, if the fre

quency is larger than 60 % of the nominal frequency. If “Voltage

measuring” (parameter 1851 Ä p. 41) is configured to a three

phase measurement, the slow voltage increase alarm is monitoring

the individual three-phase voltages according to parameter “AND

characteristics”

n case of undervoltage some grid codes require a special moni

toring function to avoid the import of inductive reactive power at the

interchange point. The QV monitoring is a function of voltage and

reactive power. To prevent malfunction, a “Minimum current”

(parameter 3287 Ä p. 67) must be configured.

QV monitoring is triggered if the following conditions are fulfilled:

(Refer to Fig. 38 for details)

n QV monitoring is configured to “On” (parameter 3292 Ä p. 67)

n Measured reactive power is higher than the configured “Reac

tive power threshold” (parameter 3291 Ä p. 67)

n Measured average current is higher than the configured “Min

imum current” (parameter 3287 Ä p. 67)

n Measured voltages are below the configured “Limit under

voltage” (parameter 3285 Ä p. 67)

As a result Timer 1 and Timer 2 are starting. If the delay time

“Delay step 1” (parameter 3283 Ä p. 67) has exceeded, the speci

fied relay for step 1 is energized. If the delay time “Delay step 2”

(parameter 3284 Ä p. 67) has exceeded, the specified relay for

step 2 is energized.