BS EN IEC 60255-187-1:2021

What is BS EN IEC 60255-187-1 about?  

BS EN IEC 60255-187-1 covers the differential protection function whose operating characteristic can be defined on a bias-differential plane. It includes specification of the protection function, measurement characteristics, compensation of energizing quantities, additional restraint or blocking methods (for overexcitation and magnetizing inrush), starting and time delay characteristics.

BS EN IEC 60255-187-1 defines the influencing factors that affect the accuracy under steady-state conditions and performance characteristics during dynamic conditions. It also includes the test methodologies for verifying performance characteristics and accuracy.  

BS EN IEC 60255-187-1 also includes current transformer requirements for the protection functions. 

Note 1: BS EN IEC 60255-187-1 does not specify the functional description of additional features often associated with biased differential relays such as current transformer (CT) supervision (CTS), switch onto fault (SOTF) and detection of geo-magnetically induced currents (GIC). 

Note 2: BS EN IEC 60255-187-1 does not cover differential relays designed for bus bar protection (including high impedance differential protection and low impedance differential protection) or line protection. 

Note 3: Additionally, BS EN IEC 60255-187-1 does not explicitly cover generator incomplete longitudinal differential protection, generator split-phase transverse differential protection, self-balancing or magnetic balanced protection scheme, differential protection of phase-shifting transformers, directional restricted earth fault protection, railway transformers, convertor transformers and reactors.  

Who is BS EN IEC 60255-187-1 for?  

BS EN IEC 60255-187-1 on the protection of motors, generators and transformers is for: 

• Manufacturers of motors, generators and transformers 
• Suppliers, importers and dealers of motors, generators and transformers 
• Service providers for motors, generators and transformers 
• Device designers for motors, generators and transformers 

Why should you use BS EN IEC 60255-187-1?  

 BS EN IEC 60255-187-1 gives you unrestrained differential protection functions traditionally combined with the restrained (biased) differential element to form a single differential relay, in order to protect motors, generators and transformers. 

BS EN IEC 60255-187-1 provides you with the minimum requirements for functional and performance evaluation of (longitudinal) differential protection designed for the detection of faults in AC motors, generators and transformers. It also defines how to document and publish performance test results, which makes it feasible to understand for any type of end user. 

With help of BS EN IEC 60255-187-1 you can ensure performance characteristics and accuracy. 

What’s changed since the last update?  

BS EN IEC 60255-187-1 together with IEC 60255-187-2 and IEC 60255-187-3, cancels and replaces IEC 60255-13. BS EN IEC 60255-187-1 includes the following significant technical changes with respect to IEC 60255-13: 

• IEC 60255-13 has been significantly revised to follow the common structure of the functional standards for protection relays (IEC 60255-1xx series). IEC 60255-187-1 has been developed to address the restrained and unrestrained differential protection of motors, generators, and transformers. The revisions include a detailed description of the functions including the performance specification, testing, and documentation requirements.