Impact of Very Severe Cyclone “Nisarga” on Mumbai Tata Power System Operation

Impact of Very Severe Cyclone Nisarga on Mumbai Tata Power System Operation

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Naresh Yadav ,Nikhil Telange , Milind Gole , Devanand Pallikuth, Deepak Mhase

Power System Control Center

Tata Power, Trombay Thermal Power Station Chembur -Mahul Mumbai 400074 India

AbstractNisarga was the strongest tropical cyclone to strike the Indian state Maharashtra in the month of June 2020. It was also the first cyclonic impact to Mumbai. since Cyclone Phyan in year 2009. As a result of depression in the Arabian sea, cyclone originated and moving towards north on 2nd June-2020, the India Meteorological Department (IMD) upgraded their system to track the movement of cyclonic storm and assigning the name Nisarga. Pre-preparedness by all utility and load despatchers prevented for severe loss to the electrical system. This paper includes impact of Nisarga Cyclone on power system operations across all facets in Mumbai at Maharashtra i.e. generation, transmission, distribution system.

Keywords India Meteorological Department (IMD), Western Region Load Dispatch Center (WRLDC), Maharashtra state Load Dispatch Center (MSLDC), Emergency Restoration System (ERS), Very Severe Cyclonic Storm (VSCS)

1. INTRODUCTION

Impact of Cyclone Nisarga that is hit on seacoast located at Alibaug in Maharashtras Raigad district on Wednesday afternoon with wind speed of up to 120 kmph on 3rd June 2020, on power system operation. Power system operation is very sensitive to slight changes in weather conditions (temperature, rainfall etc.) that has been impact across all facets i.e. generation, transmission, distribution, and power system restoration. Also, with modern power systems being interconnected with tie lines and disturbances caused by such a severe climatic change could be catastrophic for entire regional grid, the nature of power system being such that it leaves very slightly margin for reactive control due to high disturbance.

Indian Metrological Department (IMD) published a yellow warning for a cyclonic storm over east central Arabian sea at 1440 hrs. on 01stJune 2020 that is likely to cross north Maharashtra and South Gujarat coast between Harihareshwar (Raigad, MH) and Daman during afternoon of 03rd June 2020. As per the IMD, there were heavy to very heavy rains forecasted for remote places over South Konkan, Goa, Daman & Diu, Dadra Nagar Haveli, South Gujarat and North Madhya Maharashtra on 03rd and 04th June 2020.

The forecasted track is as under:

Fig 1: Shows the satellite image of Nisarga the super-cyclone

Fig 2: gives the track of the same over the period based on meteorological data.

From the above diagram, it is observed that the geographic location of various districts such as Ratnagiri, Sindhudurg, Raigad, Thane, Mumbai, Palghar, Pune, Ahmednagar, Aurangabad, Nashik, Malegaon, Dhule, Nandurbar and Jalgaonare within the Cone of Uncertainty.

2. THE OVERALL SYSTEM CONFIGURATION OF MUMBAI TRANSMISSION NETWORK

The Mumbai Power System is interconnected with Maharashtra State grid at three locations (Trombay, Kalwa Borivli, Boisar). The State grid is further interconnected with

Gujarat and Madhya Pradesh State grids through 400 kV and 220 kV interstate tie lines.

The Tata Power Company forms an important component of the Maharashtra State grid. The present installed capacity of Tata is 1377 MW and Adani 500 MW in Mumbai. Tata power generating and receiving stations are strongly interconnected through 220 kV & 110 kV overhead and underground transmission lines and 33/22/6.6 KV distribution network.

Fig 3: Mumbai Tata Power Transmission Layout with Tie line connection

The distribution node at PSCC is responsible for handling the TPC-D load of direct consumers at 33, 22 and 11 KV levels. Distribution node has total 6 zones:

1) North suburbs (North) 2) West (Central)

3) Metro (South-Central) 4) Urban(South)

5) East 6) City

Fig 4: Mumbai Tata Power Distribution Layout

3. DIRECTIVES PREVENTIVE MEASURE TAKEN BY WRLDC/MSLDC BEFORE LANDFALL OF CYCLONE

For All Users:

Cyclone is likely to have impact on transmission distribution infrastructure and may result in tripping/break-down of the same. Substation & Line O&M personnel and Protection Engineers to remain alert in Sub- Stations and Power Stations to analyse the cause of tripping. Healthy elements of the network shall be quickly taken into service in consultation with SLDC to ensure system integrity.

Planned shut-downs in North Maharashtra and MMR region shall be avoided on 3rd and 4th June 2020.

System restoration procedure/program shall be kept readily accessible at Power Stations & Sub-Stations.

SCADA/IT/Communications teams at MSLDC / MSETCL /TPC/AEML shall remain alert to quickly restore voice and data communication from substation/power station to MSLDC/RLDC.

For Transmission Licensees:

High voltage is likely to be experienced consequent to demand crash. All switchable shunt reactors shall be taken in service to control voltage. Shunt capacitor banks in sub- transmission system shall be taken out of service to control high voltage.

In case of high voltage (>410 kV), bus reactors shall be taken in service in consultation with MSLDC. If required, EHV lines shall be manually opened for Voltage regulations in consultation with MSLDC. SLDC Maharashtra shall inform all the switching actions to WRLDC during cyclonic storm.

Lightly loaded and redundant EHV lines could be taken out of service for voltage control wherever feasible. Switchable lines reactors wherever available shall be utilized for voltage control.

Single phase auto reclosure in all EHV lines above 220 kV shall be kept enabled to avoid line outage on transient faults.

Sub-stations and lines feeding traction supply shall be closely monitored. In case of interruption, restoration shall be done on priority.

Transmission lines connected to Nuclear power stations of Tarapur shall be monitored closely and in case of tripping, best efforts shall be done to extend the supply within 30 minutes to avoid poisoning of nuclear units.

Healthiness of islanding schemes Mumbai System & Urban shall be ensured. Load identified for island vis-à-vis generation in the identified island shall be monitored in real time to enhance probability of survival of the island. Adequacy of internal generation in Mumbai Island shall be ensured.

All line and Generation unit outage plan were deferred during period

Healthiness of UFR (Under frequency Relay) and df/dt load shedding scheme shall be ensured by respective Transmission licensee.

Emergency restoration system shall be kept ready by transmission utilities for deployment in cyclone prone areas.

Loading of transmission lines and ICTs, in cyclone affected areas shall be closely monitored and suitable measures shall be taken to ensure adequate margins to handle contingencies.

For Generation Companies:

Fast ramping gas and hydro units shall be deployed to manage loss of generationdue to tripping of thermal stations or loss of RE generation. Unit commitment for 2nd, 3rd and 4th June 2020 shall be reviewed in the light of weather forecast updates.

Generating units on bar shall absorb reactive power within its capability curve during high voltage (>410 kV)

Synchronous condenser facility available at Koyna shall be deployed for voltage control as and when required on instructions of MSLDC

Adequate fuel stock for Diesel Generator set shall be ensured at generating stations having black start capabilities. Healthiness of the black start DG facility shall be ensured.

For Distribution Licensees:

Demand in Maharashtra is likely to reduce because of cyclone. Load Management Cell, MSEDCL, PSCC Tata Power & BCC Transmission, AEML in coordination with MSLDC shall monitor the demand & drawl pattern and take adequate measures to maintain load generation balance and shall be in communication with MSLDC/RLDC in case of any contingency.

Distribution utilities shall explore facets in Real-time market to maintain interchange as close to schedule as possible to control deviations from schedule.

High voltage is likely to be experienced consequent to demand crash. All switchable shunt reactors shall be taken

in service to control voltage. Shunt capacitor banks in distribution system shall be taken out of service to control high voltage.

Load identified for island vis-à-vis generation in the identified island shall be monitored in real time to enhance probability of survival of the island.

Suitable advisory to ensure adequacy of back-up power supply in the areas under predicted cyclone path shall be issued to establishments serving critical essential load such as hospitals, district headquarters, communication, etc.

For RE Generators/QCAs:

Wind and Solar PV generating stations shall provide reactive support to control voltage at the respective pooling stations within their capability.

RE developers shall be alerting to ensure availability of telemetry to MSLDC.

RE generation shall be curtailed on instructions of MSLDC in case of threat to grid security due to high frequency consequent to large load throw off.

Schedules shall be carefully submitted by all the QCAs considering impact of Cyclone. All the revisions shall be utilized judicially for most accurate forecasts, as under reduced demand conditions and abnormal weather conditions, RE generation plays critical role in Grid management.

4. CONTINGENCY PLAN TAKEN BY TATA POWER BEFORE LANDFALL OF CYCLONE AT MUMBAI

The demand was expected to reduce drastically prevailing cyclone conditions hence close monitoring of demand and drawl pattern was required for maintaining generation load balance

Thermal generation may be dropped on instruction by WRLDC / SLDC below technical minimum for frequency control

All Thermal power stations shall units were kept on FGMO / RGMO with droop setting between 3-5%.

Operational staff at Hydro stations shall be on alert for quick generation variation and supply was restoration after any tripping

Healthiness of DG sets to be ensured at Hydro stations for black start readiness.

Due to inclement weather conditions, all the operational staff at Receiving stations was on alert for quick response followed by any tripping for supply restoration.

High voltage was likely to be experienced after change in weather conditions and demand crash and preventive measures such as cutting out of capacitor banks / change in tap of Transformers (OLTC) was kept active.

Guidelines issue to all consumer for Cut-OFF capacitor at their end and TATA Power Mumbai manage voltage profile and reactive power as per line loading and system condition.

Extra manpower was deployed at all stations as part of crisis management.

No outages of power system element were planned for 3rd and 4th June 2020 for system security

Material movement from stores to site and vice versa were restricted for the next 2 days.

Special attention was given to Over Head sections and H frames in the zones. Action plan was prepared by the zone in case of damage to the line. Transmission team to be apprised to be in readiness

All voice and data communication availability were maintained

Islanding Preparedness was checked and kept ready:Bhira Islanding – In above continuous trippings:7. KEY LEARNING:8. Conclusions

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