b'Partner News Spring 2021 31EnterpriseThe process of transferring existing protection settings from old electromechanical relays to numericalrelays requires extra diligence.Although the latter method isGiven that the practical imbalance considered as modern and reliable, thecharacteristics of the synchronous burden of calculating new protectionmotor are unavailable, the more settings cannot be avoided.conservative setting (TDM=0.01) Aside from calculating the new parametersis deemed as acceptable. correctly, additional application specific design work is required to ensure thatUltimately, throughout the process a the intuitive numerical relay does notprotection design engineer has to maintain malfunction. Again, considering out ofa balance between retaining previous step protection for synchronous motors,settings and underutilising an intuitive in many cases for the element to functiondevice. Thus, a designer has to understand correctly a timed block function is required.how the concepts of existing design match the other systems apart from protection The reasoning behind the blocksystem and include new technologies in function is that when the motor startsthe existing system as improvement. before excitation is applied, it runs as an asynchronous motor, which is inherently out of step. The protectionYurinov Mambau is a Graduate Electrical Engineer at Excitation Engineering element blocks the relay from operatingServices having started in 2020. She was awarded a distinction for an MSc in until the motor is synchronised.Electrical Power Engineering from Glasgow Caledonian University. Additionally, she has a BSc in Electrical Engineering from the University of Zimbabwe. Due to Another area of concern that tends toher keen interest in innovative and groundbreaking technology she is currently affect the protection retrofit process isan observing member at CIGRE B4.81 working group since June 2020.the variations in relay characteristics, particularly speed of operation. ForExcitation & Engineering services specialise in the design, commissioning, example, during secondary injection testsinstallation and maintenance of excitation and synchronous machine control conducted by Excitation & Engineeringand protection systems. We have designed and manufactured systems for a Services it was observed that the currentnumber of high-profile utilities. Our industry expertise, combined with a growing unbalance element (46) element of areputation for excellence and value, has seen our engineers working on major numerical relay with a TDM value of 0.01international projects. Our professional design and consultancy service is backed yielded a slightly faster tripping time thanby comprehensive hands-on support covering emergencies/breakdowns, routine an equivalent electromechanical phasemaintenance, system testing and diagnostics, up to date system replacement unbalance element (approximately 100ms).and training. In 2020, we won Excellence in International Business and Business However, the next TDM value 0.02 yieldedof the Year; at the Greater Birmingham Chamber of Commerce awards. a slower tripping time.'