Introduction; Hardware Description; General; Figure 1 - Dad-N Numerical High Impedance Protection - Siemens 7SG12 DAD-N Manual

1

Introduction

The DAD-N relay represents an integration of the protection elements required to provide a complete
Numerical High Impedance protection, with additional auxiliary and backup elements available to provide
integrated scheme solutions. The basic relay is a single differential zone as shown below. Other models
are also available which incorporate multiple zones of protection which may be used together with logic
schemes to form more complex busbar protection zones with check zone capability.
N
A
B
C
DAD-N-101
High Impedence Numerical Differential
CT 87/50
AN1C1 - C3
50
Figure 1 – DAD-N-101 Numerical High Impedance protection
2

Hardware Description

2.1 General

The structure of the relay is based upon the Modular II hardware and software platform illustrated in Figure
2 where the required cards plug in from the front after opening the front fascia. Modules are interconnected
by means of ribbon cable. The basic relay is supplied in a standard Epsilon case size E8. The Modular II
design provides commonality between products and spare parts across a range of protection and control
relays including Duobias, Ohmega, Delta, Tau and Iota.
©2010 Siemens Protection Devices Limited
High Impedence Differential
Protected Zone
R
87/50
-1 -2
7SG12 DAD N Description of Operation
R R
AN1
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Chapter 1 Page 3 of 14