by Dr. Murty V.V.S. Yalla, President at Beckwith Electric Co., USA

International Electrotechnical Commission (IEC) Technical Committee 95 Measuring Relays and Protection Equipment set up a maintenance team (MT4) in 2006 to revise the existing functional standards and develop new standards.

Since their first meeting in Largo, Florida in Oct 2006 MT4 met 9 times in various countries. The last meeting was in Beijing, China from April 26th to 29th, 2010 which was hosted by MT4 member Mr. Jaiwei HU, General Manager of Beijing Unisplendour M&C Co Ltd. In addition to the MT4 members the Beijing meeting was also attended by Dr Yaping Li, Chairperson of the TC95 (Figure 1). Initially MT4 started working on the following standards:

• IEC 60255-121 Functional requirements for distance protection
• IEC 60255-151 Functional requirements for over/under current protection
• IEC 60255-127 Functional requirements for over/under voltage protection

IEC 60255-151 was published in  Oct 2009 which supersedes IEC 60255-3. IEC 60255-127 was published on April 27, 2010 and it also superseded IEC 60255-3. IEC 60255-121 document is in the CD (committee draft) stage and it is expected to be published in the next 18 months.

In the 2008 IEC TC 95 meeting in Sao Paulo, Brazil new work was assigned to MT4 to update IEC 60255-8 Thermal Electrical Relays and IEC 60255-13 Differential Relays. The work on these standards is in the initial stages.

A brief overview of one of the recently published standards (IEC 60255-151) is presented here.

This standard specifies minimum requirements for over/under current relays. It includes protection function specification, measurement and time delay characteristics. The standard defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions. The test methodologies for verifying performance characteristics and accuracy are also included in this standard. The IEC 60255-151 includes a total of six dependent time curves three from IEEE standard C37.112 and three from IEC 60255-3 (superseeded by IEC 60255-151). Example of the constants for curves included in the standard are shown in Table 1.

The cooperation between the IEEE and the IEC allows international standards to be developed that have a wide spread usage in North America as well as the rest of the world.  One major difference between IEC 60255-151 and its predecessor IEC 60255-3 is the inclusion of dependent time reset characteristic.  The dependent time reset characteristic allows the digital multifunctional relays to properly coordinate with electromechanical induction disc overcurrent relays.

The maintenance team 4 of the TC 95 has 29 delegates from 14 countries. The present membership is as follows:

• Convener: Dr. Murty Yalla (USA)
• Mr Philippe Alibert (France)
• Dr. Alexander Apostolov (USA)
• Mr Boris Bastigkeit (Austria)
• Mr Phil Beaumont (Great Britain)
• Mr Andrea Bonetti (Sweden)
• Mr Gustavo Brunello (Canada)
• Mr Roberval Bulgarelli (Brazil)
• Mr Diego De Martis (Italy)
• Mr Zoran Gajic (Sweden)
• Mr Stig Holst (Sweden)
• Mr Jiawei Hu (China)
• Mr Kazuyuki Hyodo (Japan)
• Mr Hachidai Ito (Japan)
• Mr Takahiro Kase (Japan)
• Mr Yoshihoro Katayama (Japan)
• Mr David Keeling (Great Britain)
• Mr Lauri Kumpulainen (Finland)
• Dr. Siegfried Lemmer (Germany)
• Mr Rene Lord (Canada)
• Mr A.P Millard (Great Britain)
• Dr. Kornél Pál Petri (Hungary)
• Mr Norbert Schuster (Germany)
• Mr Pascal Tantin (France)
• Mr Giuseppe Vianello (Italy)
• Mr Serge Volut (France)
• Mr Björn Westman (Sweden)
• Mr Xicai Zhao (China)
• Ms Manyong Zhao (China) 

Biography:

Dr. Murty V.V.S. Yalla   has been with Beckwith Electric Co. since 1989 and presently holds the position of President.  He received a Ph.D. in Electrical Engineering from the University of New Brunswick, Canada in 1987. Dr. Yalla taught and conducted research on digital power system protection at Memorial University in Newfoundland, Canada, and holds five U.S. patents in the areas of digital controls and protective relays. Dr. Yalla is a US delegate and the Convener of the International Electrotechnical Commission (IEC) Technical Committee 95 MT4.  He is a US delegate to CIGRÈ Working Groups B5.04, and B5.05.

He is also a member of the North American Electric Reliability Corporation (NERC) System Protection and Control Subcommittee (SPCS). He is a Fellow since 2006 and an active member of the IEEE Power System Relaying Committee (PSRC) for the past 20 years.

Dr. Yalla is presently the Vice Chair of the Rotating Machinery Protection Subcommittee of the PSRC. He was the chairman of the working group which developed IEEE Standard C37.102-2006 and co-authored an IEEE PES tutorial on the "Protection of Synchronous Generators." He chaired the working group which received the IEEE (PES Working Group Recognition Award for an outstanding technical report in June 2004. He also received the IEEE Florida Council Outstanding Engineer Award in 2005.