7SR11 & 7SR12 Description Of Operation
©2012 Siemens Protection Devices Limited Chapter 1 Page 7 of 76
Section 1: Introduction
This manual is applicable to the following relays:
• 7SR11 Overcurrent and Earth Fault Relay
• 7SR12 Directional Overcurrent and Directional Earth Fault Relay
The ‘Ordering Option’ Tables summarise the features available in each model
General Safety Precautions
1.1 Current Transformer Circuits
The secondary circuit of a live CT must not be open circuited. Non-observance of this precaution can
result in injury to personnel or damage to equipment.
1.2 External Resistors
Where external resistors are connected to the relay circuitry, these may present a danger of electric
shock or burns, if touched.
1.3 Front Cover
The front cover provides additional securing of the relay element within the case. The relay cover
should be in place during normal operating conditions.
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