SLDC Control Room Case Study
Twice Grid Failure Event on Jan 2nd, 2010
From Power Controller Desk
Northern Region experienced a partial grid disturbance on the night of 1st – 2nd January, 2010 at 03:01 hrs. in which power supply in Punjab, North Haryana, HP, J & K and UT Chandigarh sub-system was affected. This was followed by another partial disturbance almost on the similar lines, during the late evening hours on the same day i.e. 2nd January, 2010 at 21:54 hrs. leading to Load loss of about 9000MW & Generation Loss of about 5159 MW(as per NRLDC report.) was reported in Northern region.
After initial disturbance during morning Hours, system was normalized during evening Hours.
Subsequently in this incident which took place between 2144 to 2154 hrs on the same day, a number of 400 kV and 220 kV lines feeding Punjab/Haryana/HP/J&K/UT Chandigarh sub-system had tripped (as per NRLDC reports). The incident initiated with a combination of faults at Bamnauli/Bawana and inadequate safety net in the separated sub-system leading to its collapse.
Himachal Pradesh which is connected through various interstate Links was left with only one link i.e. 220 KV Khodri-Majri (Uttarakhand System). Following is the list of interstate lines connecting H.P. which tripped simultaneously:
1. 220 KV Panchkula-Kunihar
2. 220 KV Panchkula-Baddi-Kunihar
3. 220 KV Jalandhar-Hamirpur-I
4. 220 KV Jalandhar-Hamirpur-II
5. 220 KV Dehar-Kangoo
6. 220 KV Jassure-Pong
7. 220 KV Jassure-RSD
8. 220 KV Jassure-Bairasiul
9. 132 KV Dehar-Kangoo
10. 132 KV Hamirpur-Chohal
With this, all connected Load a/w Running Generators tripped leading to load loss of about 750 MW & Generation Loss of about 285 MW. 400KV Baspa-Jhakri-I&II evacuating power of Baspa Power House also tripped at the same instant.
Detail of running Units under control of HPSEB which tripped is as under:
Larji Power House 32 MW
Bhaba Power House 40 MW
Bassi Power House 15 MW
Giri Power House 18 MW
Baspa Power House 140 MW
Micros(Unmonitored) 35 MW
Chart illustrating Demand Wise Normal & disturbance condition
Chart illustrating loss of Generation for the State
at 22.00 Hrs. on 2nd January 2010
Strategy Adopted:
Immediately, after condition of black out was faced, next came the most challenging task for the control room operators. Lightning entire State with Single Link available & that too the one which is usually considered the weakest link of our H.P. Grid-220KV Khodri-Majri, which was feeding Industrial Area of Kala Amb through only one Line surviving in H.P. Network, 132KV Giri-Kala Amb.
On contacting SLDC, Rishikesh for making them aware of situation of virtually complete Black out in Himachal Pradesh & ascertaining uninterrupted supply through Khodri, restriction of drawl to the limit of 50MW was imposed by them, yet another problem.
While in restoration process main points to be kept in mind were that of keeping Voltages under control as high voltages hamper synchronizing of Generators & closing of Circuit Breakers, as closing of Breakers under High Voltage condition increases the re striking voltage for the breaker enhancing the chances of Trippings.
As Transmission Network was to be charged through Giri(Nahan) to near & far end areas of the state like Solan, BhabaNagar, Hamirpur, Kullu, Jassure etc, correct combination of Generation along with Load was required. Hence keeping all points in mind restoration process was initiated immediately.
Summary of Events:
21:55 Hrs. Supply Failed through all inter state points except 220KV Khodri-Majri leading to Generation loss in all running units at Bhaba, Larji, Ghanvi, Bassi along with Load loss in entire state except Kala Amb.
22:10 Hrs. Unit-II of Giri Power House synchronized with Khodri.
22:18 Hrs. 132 KV Paonta tripped from Giri.
22:20 Hrs. 132 KV Bus Coupler closed from Giri & Supply restored upto Solan after ensuring that all outgoing feeders at Solan are in Open state.
22:29 Hrs. Khodri Supply restored upto 220KV Sub station, Kunihar after ensuring that all Outgoing feeders at Kunihar are in Open State.
22:34 Hrs. Supply restored up to Bhaba Power House by closing 220KV Bhaba-I,II for synchronizing its unit. Supply extended through Kotla to synchronise Ghanvi & Andhra.Kotla allowed to draw load.
22:40 Hrs. Supply to 132 KV Shimla restored through circuit-I.
22:45 Hrs. Supply restored to 66KV Totu.
22:55 Hrs. 33 KV Bharari feeder closed at Shimla.
22:55 Hrs. 132 KV Kangoo-Kunihar S/C & 132 KV Kangoo-Kunihar D/C closed at Kunihar after ensuring that all outgoing feeders at Kangoo are in open State & Supply extended to Larji power House through 132KV Kangoo-Larji-I&II for synchronizing its units.
23:05 Hrs. Unit-II of Bhaba Power House on Bar with 40 MW Load. It was decided to feed Shimla area thereafter.
23:07 Hrs. Gumma feeder closed at Shimla.
23:07 Hrs. 132 KV Kunihar-Shimla-II restored.
23:08 Hrs. Load to Subathu & Local Kunihar restored through Kunihar.
23:12 Hrs. Shoghi & Khalini feeders closed at Shimla.
23:13 Hrs. Dhami & Ashwani Khud feeders closed at Shimla.
23:15 Hrs. 132KV Kunihar-Darla closed from Kunihar.
23:30 Hrs. 132KV Kangoo-Hamirpur-I&II were closed at Kangoo after ensuring that all outgoing feeders at Mattansidh are in open state.
23:35 Hrs. Unit-I of Larji Power House on Bar with 32MW Load.
23:35 Hrs. Supply restored to 132KV Substation Anu after ensuring that all outgoing feeders are in open state.Suppy was immediately extended to 132KV Substation, Bassi Power House for synchronizing its unit.
23:38 Hrs. After Generation was available from Larji, Loads through 132KV Substations Bajaura & Bijni were restored immediately through Kangoo/Larji.
23:40 Hrs. Load to Local Solan Town & Parwanoo restored at Solan.
23:43 Hrs. Baspa Unit Synchronised initially with 30MW load gradually icreased to 80MW on request of NRLDC.
23:45 Hrs. 132KV Bassi-Shanan feeder energized.
23:51 Hrs. As Panchkula supply was available up to Baddi & Kunihar, after clearance from NRLDC, Baddi was allowed to draw about 40MW load. However, due to restriction on Panchkula & Khodri as well it was decided not to integrate Panchkula with Khodri supply.
23:55 Hrs 132KV Barotiwala-II closed from Kunihar for station Supply.
23:55 Hrs. Load to Local Hamirpur Town restored at Anu.
23:58 Hrs. 33 KV Barsar feeder energized.
24:00 Hrs. 132KV Dehra-I&II closed at Mattansidh after ensuring all outgoing feeders at Dehra are in Open state.
00:05 Hrs. Supply restored at 220KV Jassure via 132 KV Mattansidh-Dehra Link & 220KV Bus charged. Clearance given to Load 220/33 KV Transformer & 132KV System via Dehra owing to High voltage condition.
00:05 Hrs. Unit-II of Bassi Power House synchronized with 8MW Load.
00:15 Hrs. 220 KV Pong, Bairasiul & RSD feeders opened at Jassure to control High Voltage.
00:25 Hrs. 220/132 KV Transformer Bank-I&II closed at Mattansidh & held OK.
00:25 Hrs. 220 KV Dehar Supply restored at Kangoo. With this 132KV ACC-I&II alon with H.P. Area closed.
00:26 Hrs. Clearance to GACL to draw load.
00:27 Hrs. 220 KV Jalandhar-I&II closed from Hamirpur end.
00:29 Hrs. 132 KV Dehar Supply restored at Kangoo & came in parallel operation with 220 KV Dehar Supply at Kangoo.
00:35 Hrs. All 33KV feeders viz. Tauni Devi, Sujanpur, Ladraur, Bangana, Nadaun energized at Anu.
00:40 Hrs. 220 KV Jalandhar successfully closed from Jalandhar under High Voltage Conditions. Now Jalandhar Supply came in integrated operation with Khodri Supply.
00:40 Hrs. Clearance for full load to Solan.
00:48 Hrs. With conditions slightly under control 220KV Baddi was closed from Kunihar & 220KV Panchkula closed from Kunihar, now integrating it with Jalandhar & Khodri Supply.
00:40 Hrs. 132KV Darlaghat closed from Kangoo.
All intra state Links at this point of time were intact & charged, thus making state conditions controlled. Clearance for Loads was released to all Substations after this.
01:06 Hrs. 220 KV Jassure-Pong Closed.
01:18 Hrs.With No Drawl available from Jassure & increasing load from Kunihar transformer, 132KV Bus coupler at Kunihar opened at 01:18 Hrs. thus creating two systems viz Panchkula and Jalandhar-Khodri.
02:25 Hrs. Due to no drawl from Jassure & Increasing Drawl from Khodri restrictions at Kala Amb & Local Giri to the order of 5-10 MW affected.
02:30 Hrs. Load available from Bairasiul after charging of 220KV Pong-Bairasiul circuit. Thus normal load allowed to Kala Amb & local Giri.
04:20 Hrs. 132KV Bus Coupler at Giri opened to avoid Overloading of Khodri system, thus making all supplies in radial mode.
06:25 Hrs. 132KV Hamirpur-Chohal restored.
Points of Reference Compiled by Er. Vikas Sharma
P.S:
The process & operations described here are not sufficient to describe the practical conditions & mental State of Control Room operators faced when the only priority was restoration of supply to all areas of the State.
Shift on Job – GROUP-C (NIGHT SHIFT)
Er. K.S. Sambyal, Sr. Executive Engineer
Er. Vikas Sharma, Assistant Engineer
Er. G.R. Mastana, Additional Assistant Engineer
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