Applications; Introduction; Basic Requirements; Operating Time Delay - GE KVGC 202 Technical Manual

Technical Manual
KVGC202
SD5=1 – setting group 2. If SD6=1 then reverse current will automatically select group 2
settings.
Note:
Link [SD4] must be set to "1" to make the second setting group active. Then manual
selection of Group 2 can be made by setting link SD5=1 or a reverse current will select
Group 2 if link SD6=1.
4.4

ApplicatIons

4.4.1

Introduction

As the loads connected to a distribution network vary through out the day, so the do the
voltage drops in the conductors and transformers.
unacceptable variations in voltages supplied to consumers.
transformers in primary substations and above are generally fitted with on load
tapchangers, usually on the HV side.
arrangements that adjust the transformer turns ratio, typically in steps of 1.25% or 1.43%,
whilst the transformers are in use and carrying a load.
The operation of the tap changer mechanism is automatically controlled by a voltage
regulating relay (VRR) such as the KVGC202. A VRR constantly monitors the system
voltage and initiates the tap change mechanism to Raise or Lower the voltage to be
within set limits of a desired value.
4.4.2

Basic requirements

The fundamental objective of a VRR is to control a voltage regulating transformer such
that the system voltage is maintained within set limits of ± dVs%, about a reference
voltage setting Vs.
Figure 4:
These limits define a deadband of ± dVs% of Vs which are dependent on the tap step
increment of the regulating transformer. Typically, ± dVs% = ±1% for an average tap step
increment of 1.43% on the transformer to prevent hunting.
The VRR compares the monitored system voltage with the reference voltage setting Vs
and provides raise and lower signals to the tap changer to control the system voltage to
be within the set deadband limits of ± dVs%.
4.4.3

Operating time delay

In a basic voltage regulating control relay it is necessary to incorporate a time delay to
prevent tap changes due to momentary voltage fluctuations. A short time delay provides
better regulation but results in excessive operation of the tap changer mechanism leading
to increased maintenance and hence operating costs.
If [SD4] = 0 then the group 2 settings will be hidden and group 1
will be active by default.
Basic Regulating Requirements
If unchecked this would lead to
These are motorised mechanical switching
KVCG202/EN M/H11
To prevent this the