7SR11 & 7SR12 Description Of Operation
Chapter 1 Page 8 of 88 ©2017 Siemens Protection Devices Limited
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
It is the responsibility of the user to ensure that the equipment is installed, operated and used for its intended
function in the manner specified by the manufacturer. If this is not the case, then any safety protection provided
by the equipment may be impaired.
The equipment shall be isolated or disconnected from hazardous live voltage before access to potentially
hazardous live parts is affected.
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.
External Resistors
Where external resistors are connected to the relay circuitry, these may present a danger of electric
shock or burns, if touched.
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.
Fibre Optic Communication
Where fibre optic communication ports are fitted, the lasers are Class 1 devices but recommend they
should not be viewed directly.
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