Megger SVERKER 900, Техническое руководство

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Technical Guide
Testing self-powered relays with SVERKER 900
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5.2. Testing the phase overcurrent relay.
5.2.1. Relay settings.
The phase overcurrent protection relay has the following settings in primary values
7
:
I>= 30 A
Characteristic Normal Inverse (IEC
“A”: Inverse, par. 4.1.1)
Time Multiplier (a) = 0,3
I>>= 200 A
Characteristic Definite Time
Time Delay t = 200 ms
The relay settings have been entered by using the dipswitches as shown in par. 5.1.
According to the relay manual, a current of 1A injected from the test terminals (connectors C-D) corresponds to
a primay current of 50 A (Figure 9 and Figure 2).
Figure 9.
Relationship between the “secondary test current and the primary current depending on the used
current transformer (from the WIC-
1 user’s manual [5], Copyright SEG GmbH)
As the relay will be tested with current injections from the test terminals, it is simple to get the relay
characteristics as function of the test current (terminals C-
D), because 1 A “secondary test current” is equivalent
to 50 A “primary current”.
I>_test= 30 A x (1/50) = 0,6 A
Characteristic Normal Inverse
Time Multiplier (a) = 0,3
I>>_test = 200 A x (1/50) = 4,0 A
Characteristic Definite Time
Time Delay t = 200 ms
The table below represents an overview of the values. The secondary values (S2-S1) are shown only for
reference, but they are not used for the testing procedure:
7 The secondary settings (in the relay analog inputs, connectors S2-S1) are derived from the CT ratio, which is 14,4 A / 0,075
A = 192.
I>= 30 A / 192 = 0,156 A, Characteristic Normal Inverse, Time Multiplier (a) = 0,3
I>>= 200 A / 192 = 1,042 A, Characteristic Definite Time, Time Delay t = 200 ms
These values are not fully relevant as the test will be done by using the “secondary test current method”, but they are good
to know.
The secondary values from the test terminals (connectors C-D) are 1/0,26 = 3,846 times the secondary values (see Figure 2
and the relay manual
[5]
): 1 A in the test terminals gives 0,26 A in the relay analog inputs:
I>_test= 0,156 A x 3,846 = 0,6 A, Characteristic Normal Inverse, Time Multiplier (a) = 0,3
>>_test = 1,042 A x 3,846 = 4,0 A, Characteristic Definite Time, Time Delay t = 200 ms
All of this is correct but it is not the process we will follow in this document.