Prospects for Implementation of Non-conventional Instrument Transformers
The Brainstorm block is a collection of industry experts’ opinions on actual problems. It allows specialists to look at different problems from different perspectives.
Energy professionals from around the world answered several questions about non-conventional instrument transformers:
- How would you evaluate the prospects for implementation of non-conventional current and voltage transformers? What implementation strategy of non-conventional instrument transformers should be chosen? What types of instrument transformers should be implemented in different types of bays and equipment?
- What factors prevent non-conventional current and voltage transformers from being widespread? If some of the factors are technical, what are they?
- How can you evaluate the prospects of the implementation of merging units? Will they be implemented in the future in anticipation of mass adoption of non-conventional current and voltage transformers, and if yes, for what purposes?
- What types of current and voltage transformers for what voltage levels can be used in the most reasonable way — and why?
- In what ways will mass adoption of non-conventional current and voltage transformers influence secondary systems of substations?
- How long will it take non-conventional current and voltage transformers to be massively adopted? What is their mass adoption determined by (e.g. in terms of volume or market share)?
1. It is inappropriate to talk about the prospects of all types of non-conventional instrument transformers (NCITs). In power electronics, such devices have been used for decades and have shown only their best side. At our stations, dozens of excitation systems are equipped with so-called LEM sensors, and these are just electronic instrument transformers. The application of such measuring devices in high-voltage circuits of power plants and networks is more of a confirmation of the competitive advantages of technologies used in NCIT design, compared with conventional instrument transformers, which becomes more apparent with the advent of optical instrument transformers.
However, we must not forget about the ’infantile sicknesses’ of new devices, which do not yet allow one to state that the optical electrical technologies (OET), according to their performance characteristics, have reached the level of conventional transformers.
Nevertheless, currently, I believe that optical transformers are almost ready to be used in industrial facilities of an average responsibility level. As for power plants, in the next three years, RusHydro plans to install such devices in one of the facilities currently under construction.
2. Mass introduction of optical instrument transformers is primarily hampered by the following factors:
- A lack of a single-industry, standard documentation, establishing the requirements for NCITs. During the design, testing and certification of NCITs, manufacturers currently apply regulatory documents that establish requirements for traditional current transformers/voltage transformers (CT/VT), which eliminates several potential advantages of NCITs.
- Designers lack an understanding of the qualities, characteristics and properties of new equipment; inertness in the development of new, specific knowledge, computer networks, for example, a shortage of computer-aided design (CAD) diagrams for designing digital substations.
- An absence of reference materials and methods of technical maintenance of new equipment that would define the requirements of personnel qualifications, tooling and work deadlines.
- A lack of accumulated statistics characterizing the operational indicators, in particular, life-time metrics. It should be noted that these obstacles are relevant for virtually any new solution and technology. The mechanism for overcoming these issues is traditionally based on a gradual transition from research and development (R&D) to single implementations at low-priority facilities and then extend to wider applications in the industry. Meanwhile, each next step should be followed by a period sufficient for the collection and analysis of the obtained results, namely design modification, service, personnel training and subsequent organization of the production environment at equipment suppliers. I believe that at present we are in the stage of transition to single implementations of such equipment.
3. It should be noted, that even now, without mass implementation of NCITs, it cannot be said that MUs are widely used at power facilities.
In the current understanding, an MU is a device designed to convert analogue measurements into digital form with subsequent transmission of the results via the SV IEC 61850 protocol. In this form, obviously, the need for such devices will be further reduced with the mass introduction of NCITs.
There are good prospects of such devices as bay controllers (connection controllers).
However, in addition to measuring circuits, there are also signalling and monitoring circuits, the transfer of which into digital lines of communication will remain a vital task. To solve this problem, perhaps, there are good prospects of such devices as bay controllers (connection controllers). At the same time, I believe that development of such devices is directed towards their combination with circuit breaker automatic monitoring and soon we will see the mass application of devices such as a circuit breaker automatic-monitoring control processor, which will play the role of grass-roots devices in automation systems of both stations and substations. Furthermore, the wide introduction of NCITs will only contribute to this. Specifically, in our company, there are already three realized projects of gas insulated switch-gear (GIS) automation with voltage from 110 to 330 kV, complete with application of a circuit breaker automatic-monitoring control processor.
4. Optical current transformers — for all voltage classes from 110 kV and higher, as well as for applications at generator voltages. Regarding the voltage instrument transformers, the answer is not so obvious yet, and I believe that it will take another one or two years to test the devices already proposed, to draw some conclusions.
There are many technical, organizational and regulatory issues to be resolved, but there are no fundamental obstacles here.
5. Obviously, the impact will be quite strong. As a result, we will get one device (NCIT), which will be able to provide any required number of secondary devices with measuring information, and the concept of instrument transformers (IT) system separation on current transformer (CT) cores will be history, and will remain only as a measure for ensuring reliability due to hardware redundancy. There are many technical, organizational and regulatory issues to be resolved, but there are no fundamental obstacles here.
6. It will take 5–7 years before the full-edged competition of NCITs with traditional instrument CTs becomes apparent.