Merging units – An integral part of Digital Substations with IEC 61850 process bus applications

Merging units (MU) and stand-alone merging units (SAMU) are essential components in modern electrical substations, both at transmission and distribution level. Merging units are equipped with voltage channels and current channels, which are specifically designed and engineered to convert the secondary output of traditional voltage and current transformers into an IEC 61850 Sampled Value (SV) output stream. This digitization of voltage and current measurements enables the implementation of an IEC 61850 process bus (data transmission over Ethernet networks) at a substation, providing significant benefits such as interoperability, reduced wiring, increased safety, and enhanced substation automation.

Given the risks derived from progressively incorporating digital solutions into the electrical grid infrastructure, utilities and network operators increasingly look for proof of quality when selecting new generation metering, protection and substation automation equipment. Type testing of merging units is crucial as it verifies the performance of their current and voltage channels, which is fundamental for accurate data transmission. Additionally, interoperability testing ensures that merging units can seamlessly integrate with other devices and systems within the substation.

KEMA Labs – Your trusted partner for testing and certification 

KEMA Labs actively participates in the developments within the international standardization organizations and, as a result, is committed to help ensure the safety, robustness  and performance of new generation components like Merging units (MU) and stand-alone merging units (SAMU). 

KEMA Labs can support the manufacturers of merging units by testing of prototypes or end products according to the most relevant International Standards. Our service package includes the following:

  • Hardware / environmental type testing: type testing and certification according to IEC 61869-13, IEC 60255-26 and IEC 60255-27 standards. This includes electromagnetic compatibility (EMC) tests, product safety tests, climatic tests, mechanical tests and others (burden, dimensions, markings, etc.)
  • Accuracy testing: accuracy testing of merging units according to IEC 61869-13.
  • Communication protocol conformance: protocol certification for IEC 61850 Edition 2.1 (including IEC 61869-9 Sampled Values Publish), IEC 61850 Edition 2 (including IEC 61850-9-2LE Sampled Values Publish), IEC 60870-5-101, IEC 60870-5-103, IEC 60870-5-104 and DNP3.