The network is becoming increasingly complex and there is not enough certainty of what functions may be required or even available in the future for protection to meet changing network topologies.
DNOs are often required to extend busbars and modify protection schemes for new connections and load growth projects. However current relay replacement programmes miss opportunities for the implementation of advanced protection functions, due to the trend of implementing a like-for-like replacement strategy. When replacement programs are undertaken, existing equipment is replaced with similar relays to avoid additional work for hardware modification associated with functionality enhancement. There are also multiple IEDs (Intelligent Electronic Devices) being installed on the network such as protection relays, RTUs (Remote Terminal Units), power quality meters, disturbance recorders which means multiple tools from multiple vendors need to be maintained by the field staff, creating a large training and familiarisation burden for the business.
This project will trial a new substation centralised protection system. The project method will verify and validate the use of this system for the protection of future substations. The learning generated will enable UK Power Networks and other DNOs to develop and demonstrate control functions based on such equipment in other future projects, including our proposed NIC project “Constellation”.
Instead of having local protection relays on each substation bay, a central system will be used within a substation. This system can be modified and upgraded via software and does not require new plant for the introduction of new functions or bays. There is a limit to the number of bays that a single device can support, so the system cannot be expanded indefinitely. For the purpose of the trial demonstration, the system will be installed in parallel to the existing protection scheme. It will receive measurements but the trip signals will not be connected to the switchgear. Monthly visits will be scheduled to the substation to retrieve data, analyse and compare with existing protection performance by protection experts from the technical standards team. The financial results from installation and commissioning will also provide useful information for the financial case for the device adoption. Additionally, modern standard designs adhering to IEC 61850 will be produced in order transfer the learnings from the project and subsequently facilitate a wider supplier procurement event.
Benefits
The new protection system method could save approximately £100k each time it is deployed. Based on the pace of replacement programs for the first years of RIIO-ED1 and discussions with subject matter experts, we made a hypothesis that the proposed solution can be deployed two times a year initially and scale up to five. As such the method could provide a saving of £200-500k in future value per year. This does not cover some of the intangible benefits which are:
- Less labour to install and test means less time on site so safer way to deliver work;
- Easier to upgrade protection for new connections;
- Having a futureproof system removes the need for replacement programs; and
- Less engineering time needed because of using international standardised solutions.
Learnings
Outcomes
UK Power Networks engineers have shown that the solution is a valuable method for retrofitting substation protection. A projection can be made that in cases where there is a need to retrofit the substations protection relays and also replace (or add) automatic voltage control, the centralised protection systems is a financially better solution and can achieve faster deployment compared to conventional solutions.
These outcomes can be further cemented when the evidence of performance is recorded and the pricing agreed with the suppliers. The final pricing of the equipment remains to be defined pending procurement tender events.
Lessons Learnt
The process of completing the initial engineering specifications in accordance to IEC 61850 was a considerable learning experience. A large suite of engineering documents were produced and they will form the main template for the project replication. One of the main advantages of the solution is the replicability without a need for customisation.
One of the big differentiators of the solution is the use of digital communications to carry measurements and control signals. This is a concept that the operational engineers had limited experience with and the learning process was crucial to future implementation. The engineers had to use new tools to complete the design, testing and commissioning. The experience has shown us that protection engineers will need to be proficient in communication systems in the future.
