Hydropower plants are generally considered most suitable for remote operation the world over as they are relatively simpler to operate compared to thermal or gas power plants. Moreover, digitalisation of these plants can further reduce operational complexities. In India, the Koldam hydropower plant, NTPC Limited’s maiden hydropower project in Himachal Pradesh, is the first of its kind to be operated remotely from a distance of 400 km, that is, from its control centre in Delhi. Power Line presents a glimpse of this unique project…
Background
The Koldam hydroelectric project sources water for its 800 MW power plant from the Sutlej. Delhi, Haryana, Punjab, Rajasthan, Uttar Pradesh, Himachal Pradesh, Jammu & Kashmir, and Chandigarh are the beneficiaries of the power generated at the plant. It consists of four units of 200 MW capacity each. Remote operation of the plant from NTPC’s SCOPE control centre in Delhi began in March 2018. Since that time, the success of the project has hinged on its comprehensive safety system, a well-trained response procedure, a resilient and robust communication system, and tight cybersecurity measures. The general architecture required for a control and automation system, such as field instruments and drives, input/output modules and controllers, and operator workstations and servers are present at the remote control centre in Delhi. Due to the geographical distance between the physical infrastructure and the control centre, NTPC pays particular attention to minimise latency to the operator.
Planning and implementation
In planning the project, NTPC drew from the standard practices of the hydro stations operated by Électricité de France. In France, the majority of hydro projects are grouped in clusters, and then operated remotely from common central control centres located at a significant distance from the individual dams. While the model of an Australian gas power plant was also considered for its use of multiple original equipment manufacturers (OEMs), it was deemed unsuitable because only sequences were being managed from the central location and not the drives.
Further, Koldam being the first remotely operated hydropower project in India, it was extremely important to instil confidence in stakeholders regarding remote operations. Therefore, it was initially suggested that an external consultant be engaged to develop the scheme, but NTPC itself being a technology leader, decided to develop the scheme in-house. Further, the OEM at Koldam, Bharat Heavy Electricals Limited (BHEL) had an excellent team that was able to lend its strength to the in-house development of the scheme.
Before developing the scheme in partnership with BHEL, NTPC officials visited the Koldam site to study the control room and all other associated areas of the project, like the flood room and the spillway gate room. This integrated approach was necessary to ensure a comprehensive implementation of the scheme. The development team also visited Power Grid Corporation of India Limited’s (Powergrid) National Transmission Asset Management Centre at Manesar. The facility operates 104 substations remotely, without any operation manpower on the site. Operations are primarily carried out using CCTV monitoring, and staff visits are arranged as and when required. The architecture used by Powergrid at Manesar for remote changeover, crossover and hot standby was found to be the same as that developed by NTPC for its project at Koldam.
Technology
Secured front-end communication technology was selected for the project. With this option, remote control of the HMI at the central control room of the powerhouse was made available at the remote centre. This option lent to the operator at the remote control centre the same situational awareness as that of the local operator. To enhance the situational awareness of the operator at the remote control centre, a live internet-based, high definition CCTV monitoring system was used for important areas on a separate lease line. The public address system operator at the remote control centre in Delhi was enabled to make announcements at the local centre. There is also a dedicated hotline facility with the local operator and a high speed videoconferencing facility. All other required data in the central control room of the power house has also been made available at the remote control centre.
NTPC has also established a remote interface server, which acts as an additional extended firewall between the DCS and the external network; thus the DCS is completely in an air-gapped mode. MAC binding has been extensively tested and implemented in the scheme. The system uses a secured virtual private network with a 256-bit encryption and two-factor authentication. Application whitelisting, disabling of unused ports and multiple firewalls are used to mitigate cybersecurity threats.
In sum, NTPC’s successful operation of its hydropower plant from a remote centre allows for many other possibilities, which will go a long way in shaping the operations and maintenance strategy.