IEC TS 60076-23:2018

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms and definitions
4 Service conditions
5 Selection principle
6 DC current-limiting device
7 DC current-blocking device
8 Tests
9 Packing, transportation and storage requirements
10 Nameplate specification
11 Technical documentation requirements
Annex A (informative) - Generation mechanism of DC
        bias current of power transformers caused by
        HVDC system
Annex B (informative) - Examples of harmful effects
        of DC bias current
Annex C (informative) - DC current-limiting device
Annex D (informative) - DC current-blocking device
Annex E (informative) - Information needed to calculate
        the DC bias current of transformers
Annex F (informative) - Methods of calculation of DC
        bias current voltage sources
Annex G (informative) - Application examples

IEC TS 60076-23:2018(E) specifies requirements for devices for the suppression of DC magnetic bias of power transformers and convertor transformers. It includes requirements for service conditions, structures, testing, packing, transport and storage.
The devices are connected to neutral points of power transformers and converter transformers to suppress DC bias current in the case an HVDC system is operated in monopole ground return mode or bipolar unbalanced mode. In the case of dedicated metallic return HVDC system, the devices are useful to mitigate DC stray current flowing through power transformers and converter transformers during transient conditions such as DC line fault.
This document applies to DC magnetic bias suppression devices for operation at frequencies of 50 Hz and 60 Hz on power systems having voltages above 110 kV.