Table of Contents
Advertisement
CONNECTIONS
The internal connections of the CEY52B relay are shown in Fig. 10. An elementary diagram of typical
external connections is shown in Fig. 4.
VISUAL INSPECTION
Remove the relay from its case and check that there are no broken or cracked component parts and that
all screws are tight.
MECHANICAL INSPECTION
Recheck the six adjustments mentioned under Mech anical Inspection in the section on ACCEPTANCE TESTS.
PORTABLE TEST EQUIPMENT
To eliminate the errors which may result from instrument inaccuracies and to permit testing the mho
units from a single-phase a-c test source, the test circuit shown in schematic form in Fig. 13 is recom
mended.
In this figure Rs + jXs is the source impedance, S F is the fault switch, and R L + jX L is the
impedance of the line section for which the relay is being tested. The autotransformer T A , which is across
the fault switch and line impedance, is tapped in 10 percent and 1 percent steps so that the line impedance
R L + jX L may be made to appear to the relay very nearly as the actual line on which the relay is to be used.
This is necessary since it is not feasible to provide the portable test reactor X L and the test resistor
with enough taps so that the combination may be made to match any line.
For convenience in field testing, the fault switch and tapped autotransformer of Fig. 13 have been
arranged in a portable test box, Cat. No. l02L20l, which is particularly adapted for testing directional and
distance relays. The box is provided with terminals to which the relay current and potential circuits as
well as the line and source impedances may be readily connect�d.
the user is referred to GEI-38977.
ELECTRI�AL TESTS ON THE MHO UNITS
The manner in which reach settings are made for ti1e mho units
OF SETTINGS section.
purpose
of the electrical tests in this section to check the ohmic pickup of the mho units at the settings
which have been made for a particular line section.
To check the calibration of the mho units, it is suggested that the portable test box, Cat. No. l02L201;
portable test reactor, Cat. No. 6054975; and test resistor, Cat. No. 6158546 be arranged with Type XLA test
plugs according to Fig. 14.
matic connections shown in Fig. 13 except that the type XLA test plug connections are now included.
Use of the source impedance·Rs + jXs, simulating the conditions which would be encountered in practice,
is necessary only if the relay is to be tested for overreach or contact coordination, tests which are not
normally considered necessary at the time of installation or during periodic testing.
usually be necessary in th e source connection to limit current in the fault circuit to a reasonable value,
especially when a unit with short reach setting is to be checked, and it is suggested that a reactor of
suitable value be used for this purpose since this will tend to limit harmonics in the fault current.
Since the reactance of the test reactor may be very accurately determined from its calibration curve, it
is desirable to check mho unit pickup with the fault reactor alone, due account being taken of the angular
difference between the line reactance, X L , and mho unit angle of maximum reach.
selected should be the test reactor tap nearest above twice the mho unit phase-to-neutral reach with account
being taken of tile difference in angle of the test reactor tap impedance and the unit angle of maximum reach.
From Fig. 12 it is seen that twice the relay reach of the angle of the test reactor impedance is:
To illustrate by an example let us consider the percent tap required on the test box autotransformer for
a unit that h as been factory adjusted to pickup at three ohms minimum and at a maximum torque angle of
Examples of calculations for typical settings are given in that section.
These connections of the test box and other equipment are similar to the sche
Z Min.
2Z Relay
200
Tap Setting %
0
where:
the angle of the test reactor impedance
=
9
mho unit angle of maximum reach
=
Z Min.
basic minimum reach of mho units
=
GEK 45495
For a complete description of th e test box
is brief'ly discussed in the CALCULATION
(0-8)
Cos
12
It is the
Some impedance will
The line reactance, X L ,
Advertisement
Table of Contents
