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5. INSTALLATION AND WIRING
5.1 Relay location and ambient conditions
Since every piece of technical equipment can be damaged or destroyed by inadmis-
sible ambient conditions,
the relay location should not be exposed to excessive air pollution (dust,
aggressive substances)
- severe vibration, extreme changes of temperature, high levels of humidity,
surge voltages of high arnpli tude and short rise time and powerful magnetic
fields should be avoided as far as possible.
In any event it is essential for the limits and ranges given in the section
"General Data" of the corresponding Data Sheet to be observed.
5.2 Checking the wiring
- Check that the relay has been wired in strict accordance with the correspon-
ding wiring diagram (see appendicies).
- Check that the phase references of c.t. and p.t. connections correspond.
- Check that the ratings of c.t's, p.t's and auxiliary supply agree with the
those of the relay (EW91, DC/DC converter and optp-coupler unit).
- Check that the same phase is used as R phase in all the stations.
- Check that the phase-sequence is correctly R-S-T.
5.3 C.t. connections
Generally the c.t's are wound in the sense and have the terminal designations
shown in Fig.
5
.1.
With the normal arrangement of K connected towards the
busbar and L towards the line, the secondary terminals k and 1 are connected in
strict accordance with the wiring diagram. Should the primary of a winding be
connected in the reverse sense, i.e. L towards the busbar and K towards the
line, the secondary connections to the terminals k and 1 must also be reversed.
Should there be any doubt as to the sense of any of the windings, the following
method can be used to determine the polarity of the secondaries. Terminals K
and L are connected to a d.c. source of about 4 V and k and 1 to a polarized
voltmeter as shown in Fig. 5.1. The polarity is correct, if there is a positive
deflection when the switch S is closed.
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