The Rajasthan Electricity Regulatory Commission (RERC), in a recent order, has rejected the compensation claims by a solar developer for losses incurred due to voltage fluctuations and directed them to make necessary arrangements for injecting or withdrawing reactive power per the regulations outlined by the Central Electricity Authority (CEA).

The Commission also directed the Rajasthan Rajya Vidyut Prasaran Nigam (RVPN), the state load dispatch center (SLDC), and the solar developers to take appropriate and necessary action to maintain the grid voltage within the operating limits for 200 MW (2*100 MW) solar power projects at the Bhadla Solar Park in Rajasthan.

ACME Jodhpur Solar Power, ACME Rewa Solar Energy, and ACME Solar Holding had filed a petition with the Commission requesting it to direct the respondents to comply with the Grid Code and take measures to overcome the issue of consistent voltage tripping at the 220 kV Bhadla substation and compensate the petitioners toward the loss of revenue.

The respondents included RVPN, SLDC, Saurya Urja Company of Rajasthan, Northern Regional Load Despatch Center, Northern Regional Power Committee, and the Solar Energy Corporation of India (SECI).

Background

ACME Solar Holding formed two special purpose vehicles (SPVs), namely ACME Jodhpur Solar Power and ACME Rewa Solar Energy, for the development of a 100 MW solar power project by each SPV at the Bhadla Solar Park, Phase-III in Rajasthan.

The projects supply power through a dedicated line connected to the Saurya Urja Company of Rajasthan’s 33/200 kV pooling substation, which is the interconnection point of the projects with the grid.

The pooling substation is connected to RVPN’s 400/220 kV grid substation through two 220 kV transmission lines.

The solar developers, in their submission, said since 2018, they had encountered severe voltage fluctuations at the Bhadla substation, resulting in abnormal tripping of solar inverters, damage to electrical components, and reduced power generation. The continuous under-voltage problems had hampered the generation process, preventing it from reaching its maximum capacity.

The petitioners contended that the grid disruptions and low voltage incidents at the Bhadla substation resulted from the absence of a secure and dependable transmission system, which was the responsibility of RVPN and SLDC.

However, despite repeated requests and acknowledgment of such events of grid disturbances involving voltage tripping, RVPN, and SLDC had failed to undertake measures to resolve such issues.

The petitioners had engaged Hitachi Energy India to conduct the steady state analysis and determine the cause for under voltage. According to Hitachi, the cause of the constant tripping was due to issues at the Bhadla grid substation.

Following this, RVPN officially approved installing a 500 MVAr transformer at the 400 kV Bhadla grid substation. However, despite receiving authorization in August 2022, there has been no progress on installing the transformer and STATCOM (Static Synchronous Compensator).

In response, RVPN explained that some tripping had occurred on the 220 kV line 1 (from the Pooling substation to the RVPN Bhadla substation) due to the activation of under-voltage protection by the Saurya Urja Company of Rajasthan. As of September 8, 2022, full solar generation had been recorded, and no further incidents of under-voltage tripping were observed.

RVPN also mentioned that on numerous occasions, the generator failed to provide reactive power to support the grid. Instead of assisting the grid, the generator had drawn reactive power from the grid when the grid voltage was low.

Saurya Urja Company of Rajasthan argued that considering the issues of over or under voltage on Line-01, the Commission should instruct RVPN to install STATCOM to enhance grid voltage during peak generation. This measure would prevent solar generators from experiencing energy losses and inverter tripping.

Furthermore, they requested the installation of two 25 MVAr shunt reactors to manage voltage conditions at the pooling substation connected to the main bus, with the associated development costs being covered by the solar power developers.

Commission’s analysis     

The Commission observed that the solar developers had raised the issue of grid disturbances at the Bhadla substation and requested a compensation of ₹58 million (~$697,177) for loss of revenue.

The Commission noted that dynamically varying reactive support by generators is necessary to ensure a reliable voltage level. Voltage and reactive power control significantly impact system stability, and an imbalance of reactive power, i.e., drawl during low voltage supply, can lead to voltage instability.

The state regulator noted that RVPN and Saurya Urja Company of Rajasthan had reported that the real-time reactive power injection and absorption support from the generator during under or over-voltage conditions did not meet the requirements of the CEA regulations.

It also directed the RVPN to commission the sanctioned +300MVAR, 400 kV STATCOM at 400 kV GSS Bhadla, and +100MVAR, 220 kV STATCOM at 220 kV GSS Phalodi.

It noted that the grid voltage should remain within the operating limits as specified in the CEA regulations, and the responsibility to maintain the grid voltage pertained to the solar developers, Saurya Urja Company of Rajasthan, RVPN, and SLDC.

In light of this, the Commission instructed the solar developers to establish suitable arrangements for injecting or withdrawing reactive power per the regulations outlined by the CEA.

According to the CEA, the generating station must be capable of supplying dynamically varying reactive power support to maintain power factor within the limits of 0.95 lagging to 0.95 leading.

As the petitioner shared most of the responsibility in this matter, compensation could not be awarded to the developers.

In June this year, CEA directed renewable energy developers who have applied for connectivity until April 30, 2023, to comply with CEA Connectivity Regulations by September 30 or face disconnection.

Lately, Mercom penned an article discussing the crucial aspects of grid safety, emphasizing the necessity of compensating for reactive power (grid inertia) and maintaining voltage stability.

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