ISLAMABAD: Karachi Electric (KE) has proposed National Transmission and Despatch Company (NTDC) to constitute a committee to resolve the controversy on cross-trip on 500/220 KV (NKI) grid interconnections, which resulted in less drawl of 100MW of electricity from the national grid.
Ali Imran Chaudhary, head of network control KE, has informed Managing Director, NTDC about the power utility’s earlier correspondences with General Manager South NTDC Hyderabad of November 20, 2021, and email to GM NPCC (System Operator), Islamabad on December 21, 2021, on the issue of visibility of Cross Trip Protection Scheme in Network Control Centre of KE since November 19, 2021.
According to the letter, the communication port connection between BCU and RTU for analogue signal, used for the purpose of transmitting the status of 500 KV TL feeding NKI grid and status of ATRs, has been disconnected by NTDC team.
The NTDC team maintained that the requisite information is not covered in the earlier approvals of the cross trip scheme design; therefore, it needs to be approved by the relevant quarters of NTDC. However, KE has repeatedly shared the SLD with NTDC whereby the approved scheme has been shown carrying this link.
“As explained earlier, the signals are of utmost importance for the purpose of continuously evaluating the n-1 contingency option in case of a tripping of any of the two inward 500KV circuits on which the scheme does not get activated but it provides a quick real-time benefit to both KE and NPCC to immediately control and manage the load flow on the healthy circuit to avoid any anomaly resulting in cascaded tripping in KE network,” said KE’s head of network control.
According to the power utility, in absence of this visibility and to have a contingency, KE had immediately changed its network configuration from split bus arrangement to coupled bus at KDA. This option reduced NTDC drawl from 1100 MW power to 1000 MW due to technical reasons.
KE has argued that this is causing it to operate a machine from its network out of Economic Merit Order (EMO) that results in the further back off the NTDC import during low demand period during the night. The cost burden of it would be passed on to the consumers which may not be allowed by the regulator.
Chaudhary argued that both KE and NTDC have agreed to the proposed long-term Power Purchase Agreement (PPA) and interconnection Agreement (ICA) that both will share the data in real-time at the interconnection points through SCADA. Therefore, in line with the agreement, the reason for not allowing KE to have simple visibility of the most critical scheme breakers is not understandable.
KE, he said, wants to resolve this matter amicably, for which a technical committee of NTDC and KE engineers may be formed for a better understanding of the issue and its resolution at the earliest. KE has sent the following nominations in this regard: Azizur Rehman Bozdar, head of analysis and quality assurance, and Farqud Raza, GM SCADA maintenance.
Copyright Business Recorder, 2022