Section 6 Checking the external optical and
electrical connections
About this chapter
This chapter describes what to check to ensure correct connection to the external
circuitry, such as the auxiliary power supply
, CT’s and VT’s. These checks must be
made with the protection IED de-energized.
6.1 Overview
The user must check the installation which includes verifying that the IED is
connected to the other parts of the protection system. This is done with the IED and
all connected circuits de-energized.
6.2 Checking VT circuits
Check that the wiring is in strict accordance with the supplied connection diagram.
Correct all errors before continuing to test circuitry.
Test the circuitry.
• Polarity check
• VT circuit voltage measurement (primary injection test)
• Earthing check
• Phase relationship
• Insulation resistance check
The polarity check verifies the integrity of circuits and the phase relationships. The
check should be performed as close to the IED as possible.
The primary injection test verifies the VT ratio and the wiring all the way through
from the primary system to the IED. Injection must be performed for each phase-to-
neutral circuit and each phase-to-phase pair. In each case voltages in all phases and
neutral are measured.
1MRK 504 088-UEN C Section 6
Checking the external optical and electrical connections
73
Installation and commissioning manual
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