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General
GE Multilin
The conventional, decades-old approach to testing relays utilized adjustable voltage
and current sources, variacs, phase shifters, multimeters, timing device, and the
like. In the last few years several instrumentation companies have offered
sophisticated instrumentation to test protective relays. Generally this equipment
offers built-in sources of AC voltage and current, DC voltage and current, timing
circuit, variable frequency, phase shifting, harmonic generation, and complex fault
simulation. If using such a test set, refer to the equipment manufacturer's
instructions to generate the appropriate signals required by the procedures in this
section. If you do not have a sophisticated test set, then you will need the following
'conventional' equipment:
•
Variable current source able to supply up to 40 A (depends on relay settings)
•
Variable power resistors to control current amplitude
•
Ten-turn 2 KΩ low-power potentiometer
•
Power rectifier to build a circuit to generate 2nd harmonics
•
Accurate timing device
•
Double-pole single-throw contactor suitable for at least 40 amperes AC.
•
Combined fundamental and 5th-harmonic adjustable current supply for
elements involving the 5
•
Variable-frequency source of current or voltage to test over/underfrequency and
frequency trend elements.
•
Ammeters (RMS-responding), multimeters, voltmeters
•
variable DC mA source
•
variable DC mV source
•
single-pole single-throw contactor
The simple test setup shown below can be used for the majority of tests. When the
diode is not shorted and the two currents are summed together prior to the switch,
the composite current contains the 2
harmonic restraint of the harmonic restraint percent differential elements. With the
diode shorted and the two currents fed to separate relay inputs, the slope of the
differential elements can be measured. With only I
the pickup level of any element can be measured.
http://www.GEindustrial.com/multilin
Transformer Management Relay
th
harmonic.
nd
harmonic necessary to verify the 2
connected (with a return path)
1
FIGURE 7–1: Test Setup
745
nd
7–3
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