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GENERAL
7.1.2
Testing Philosophy
7.1.3
Safety Precautions
CAUTION
CAUTION
CAUTION
CAUTION
CAUTION
7.1.4
Conventions
7–2
The 745 is realized with digital hardware and software algorithms, using extensive internal
monitoring. Consequently, it is expected that, if the input circuits, CTs, VTs, power supply,
auxiliary signals, etc., are functioning correctly, all the protection and monitoring features
inside the relay will also perform correctly, as per applied settings. It is therefore only
necessary to perform a calibration of the input circuits and cursory verification of the
protection and monitoring features to ensure that a fully-functional relay is placed into
service.
Though tests are presented in this section to verify the correct operation of all features
contained in the 745, only those features which are placed into service need be tested.
Skip all sections which cover features not included or not enabled when the relay is in
service, except for the provision of the next paragraph.
Some features such as the Local/Remote Reset of targets, display messages and
indications are common to all the protection features and hence are tested only once.
Testing of these features has been included with the Harmonic Restraint Percent
Differential, which will almost always be enabled. If, for some reasons, this element is not
enabled when the relay is in service, you will need to test the Local/Remote Reset when
testing another protection element.
Ensure the following precautions are observed before testing the relay.
HIGH VOLTAGES ARE PRESENT ON THE REAR TERMINALS OF THE RELAY, CAPABLE OF
CAUSING DEATH OR SERIOUS INJURY. USE CAUTION AND FOLLOW ALL SAFETY RULES
WHEN HANDLING, TESTING, OR ADJUSTING THE EQUIPMENT.
DO NOT OPEN THE SECONDARY CIRCUIT OF A LIVE CT, SINCE THE HIGH VOLTAGE
PRODUCED IS CAPABLE OF CAUSING DEATH OR SERIOUS INJURY, OR DAMAGE TO THE
CT INSULATION.
THE RELAY USES COMPONENTS WHICH ARE SENSITIVE TO ELECTROSTATIC DISCHARGES.
WHEN HANDLING THE UNIT, CARE SHOULD BE TAKEN TO AVOID ELECTRICAL
DISCHARGES TO THE TERMINALS AT THE REAR OF THE RELAY.
ENSURE THAT THE CONTROL POWER APPLIED TO THE RELAY, AND THE AC CURRENT
AND VOLTAGE INPUTS, MATCH THE RATINGS SPECIFIED ON THE RELAY NAMEPLATE. DO
NOT APPLY CURRENT TO THE CT INPUTS IN EXCESS OF THE SPECIFIED RATINGS.
ENSURE THAT THE LOGIC INPUT WET CONTACTS ARE CONNECTED TO VOLTAGES BELOW
THE MAXIMUM VOLTAGE SPECIFICATION OF 300 V DC.
The following conventions are used for the remainder of this chapter:
CHAPTER 7: COMMISSIONING
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
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