GE 745 Instruction Manual page 241

CHAPTER 7: COMMISSIONING
7.1.5 Test Equipment
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
• All setpoints and actual values are mentioned with their path as a means of specifying
where to find the particular message. For instance, the setpoint
, which in the message structure is located under setpoints page S2, would be
PRIMARY
written as:
S2 SYSTEM SETUP

• Normal phase rotation of a three-phase power system is ABC.
• The phase angle between a voltage signal and a current signal is positive when the
voltage leads the current.
• Phase A to neutral voltage is indicated by V
• Phase A to B voltage is indicated by V
• The neutral current signal is the 3I
any given winding.
• The ground current is the current signal measured by means of a CT in the power
transformer connection to ground.
It is possible to completely verify the 745 relay operation using the built-in test and
simulation features described earlier in this manual. However, some customers prefer to
perform simple signal-injection tests to verify the basic operation of each element placed
into service. The procedures described in this chapter have been designed for this purpose.
To use the built-in facilities, refer to the appropriate sections in this manual.
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
th
involving the 5 harmonic.
• 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
WINDING 1 WINDING 1 PHASE CT PRIMARY

(arrowhead on the "a").
an
(arrowhead on the "a").
ab
signal derived from the three phase currents for
o
GENERAL
WINDING 1 PHASE CT
7–3