Voltage Controlled Overcurrent (51V); Figure 2-3 Voltage Controlled Overcurrent - Siemens 7SR21 Manual

2.3

Voltage Controlled Overcurrent (51V)

Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
Shaped Phase Overcurrent elements 51-n should be tested for pick-up and timing before this function is tested.
The General Pickup LED can be used to assess operation of this function if other functions are disabled or if the
setting allocating General Pickup is temporarily modified.
Apply nominal 3 phase balanced voltage. Apply 3 phase balanced current at a level below the normal 51-n setting
but above the effective 51V-n setting. Ensure that the thermal rating of the relay is not exceeded. Gradually
reduce the voltage until the a-b voltage is less than the Voltage setting. Pickup LED operation can be used to
confirm the Voltage setting. If the 51V-n current setting is above the continuous rating of the relay an alternative
procedure should be used, apply test current in short duration shots with applied voltage being gradually reduced
for each subsequent shot
Apply nominal 3 phase balanced voltage. Reduce the voltage such that the a-b voltage is 110% of the Voltage
setting
©2010 Siemens Protection Devices Limited
7SR21 & 7SR22 Argus Commissioning and Maintenance

Figure 2-3 Voltage Controlled Overcurrent

V (V ), V (V ), V (V
L1 A L2 B L3
I (I ), I (I ), I (I ),
L1 A L2 B L3 C
51C, 46, 37, 49, 50CBF, 79
51-n/50-n - Self Reset
OC Phase
)
C
I
L1
I
L2
I
L3
Control Voltage
(I ) V (V )
A 12 AB
(I ) V (V )
B 23 BC
(I ) V (V )
C 31 CA
Chapter 6 Page 19 of 69