Load Checks; Tripping Tests - Siemens 7SG164 Ohmega 400 Series Manual

•
Inject at least 50% of the rated primary current into the red phase (figure 1b). Record the ammeter readings
in Table 1. Check that:-
•
Meters A, A1, A4 and relay meter readings Ia and Ix give the same reading.
•
Meters A2, A3 and relay meter readings Ib and Ic give negligible current readings.
Table 1 Current Transformer Connections
Current Transformer Secondary Levels
Current Injection
R-Y Phases
Y-B phases
R Phase
Primary Current =
Test CT Ratio =
Line CT Ratio =
Relay set CT Ratio =
Table 2 Voltage Transformer Connections
Voltage Transformer Secondary Voltages
R-N Y-N
Primary Voltage =
V.T Ratio =
Check that the supply links and fuses are arranged as follows:-
•
Trip links removed
•
Voltage transformer fuses and links inserted
•
Current transformers connected for normal operation
•
Earth links inserted
•
Measure the phase to neutral and phase to phase voltages at the relay terminals and also the phase to
phase voltages on the relay terminals and also the phase to neutral voltages on the relay display Tabulate
the results in table 2.
•
Check the phase sequence of the voltage transformer supply.

5.4 Load Checks

Directional Check
Check that the arrangement of supply links and fuses are arranged as follows:-
•
Trip links removed
•
Voltage transformer fuses and links inserted
•
Current transformers connected for normal operation
•
Earth links inserted
For this test a three-phase load current is required. Select the fascia display to INSTRUMENT MODE. Scroll in
this mode until the power flow direction meter is displayed.
This meter indicates the direction of power flow forward or reverse, of each phase. If three dashes appear on the
display, this indicates that the power flow is too small to accurately give direction. If power flows from busbars to
feeder, the direction displayed is forward.
If the directions are opposite to those expected, the relay is incorrectly connected and a careful check should be
made of the schematic and wiring diagrams and the necessary wiring alternatives made and the test repeated.

5.5 Tripping Tests

Having established the validity of the relay connections it is advisable to check the d.c. wiring to the trip and
control circuits.
To do this repeat the zone 1 secondary injection tests above with the trip links inserted. Check that for phase-
phase faults all three phases of the circuit breaker are tripped and any associated signalling and repeat relay
©2011 Siemens Protection Devices Limited
Ammeter Readings
A A1 A2
B-N R-Y Y-B
7SG164 Ohmega 400 Series Commissioning
A3 A4 Ia
B-R Va
Ib Ic Ix
Vb Vc Vx
Chapter 9 Page 5 of 6