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Power failure blues
ENERGY is one of the prime catalysts for development. It fulfils the promise of economic advancement and its availability ensures accelerated growth, both in industrial and agricultural sectors. Conversely, energy shortages lead to load-shedding and the resultant spectre of economic stagnation. To ensure a sustained progress pattern and the desired momentum of growth, it is absolutely essential that a comprehensive energy policy, both at federal and provincial levels, is carefully chalked out and meticulously executed.
What is load-shedding and how can it be avoided remains at the forefront. Shedding takes place when the energy demand of a country increases beyond the capability or supply of its generating units.
Therefore load-shedding can be defined as “blocking of customer access to energy, usually due to temporary shortage of supply.” Load-shedding is rare and is commonly applied during times of emergency or severe shortage. In most cases, the first loads a utility will shed in these conditions are loads required by industrial and commercial customers. Institutional loads are typically the last to be shed since public institutions (hospitals, schools, municipal lighting authorities, etc) are considered to be a utility’s most essential customers.
To understand the technicalities behind load-shedding, statistics with respect to the installed generating capacities in the country should be kept in mind. This will help one understand where the actual problems lies:
The tables show that the total installed generating capability of Pakistan is 16,761MW. During 2004, the maximum demand observed was about 12,000MW. One can infer that there is more than 4,000MW energy in surplus at the moment, which was planned to be exported to neighbouring countries. One wonders how despite this surplus, load-shedding continues to occur, causing heavy financial losses. The people are quick to point fingers at the water and power development authority and the ministry involved with it.
However these accusations can be misplaced, for one must understand the role of the planning and control authority in this regard — National Power Control Centre (NPCC), a sister organization of Wapda and is situated in Islamabad. Power generation and its transmission to load centres, is controlled from NPCC’s national and regional control centres. NCC controls power generation and dispatch through 4,145km, 500kv and 6332km, 220kv network from Peshawar in the north to Hub in the south. The country receives power through a secondary transmission network of 132kv and 66kv, which has more than 660 grid stations and 21,569km long transmission lines.
The major functions of NPCC include:
1. Operational control of Wapda.
2. Maintaining security, stability and reliability of the power system through frequency and voltage control.
3. Month-wise annual energy estimation.
4. Preparation and issuance of energy notifications to IPPs indicating demonstration period and maintenance months.
5. Power planning and system load forecasting.
6. Dispatching of power to all plants on economic dispatch criteria.
7. Analysis and scheduling of maintenance shutdowns of plants and transmission equipment.
8. Collection of daily data for preparation of daily and monthly reports.
These functions help one to conclude that NPCC is responsible for planned load-shedding within the country with permission from higher authorities. However, NPCC is required to consider power system objectives during overall system operation, which are:
1. High reliability.
2. High security.
3. Optimum economy.
4. Maximum safety.
Therefore if any technical issue harms the above objectives, NPCC is required to control it with effective planning. Coming back to installed generating capabilities, financial constraints compel NPCC to run the system in the most economical way. Therefore generating units must be run according to the following energy criteria:
1. Hydel power (which is the cheapest energy source).
2. Nuclear power (if any).
3. Thermal natural gas units.
4. Thermal furnace oil units.
5. Thermal High Speed Diesel (HSD) units.
In September 2004, the average hydel capability of Tarbela was reduced almost to 600MW, Mangla to 90MW and Ghazi Barotha to 700MW due to acute water shortage. There have been almost no monsoon rains in the country, and temperatures in Skardu did not rise beyond 37 degrees centigrade. Glaciers are a very important source of water for rivers and ultimately for dams. Since most glaciers did not melt this year owing to lack of rain and reduced temperatures, almost 4,000MW of energy on an average was not generated during summer.
Despite the shortage of hydel energy, one can assume that 12,000MW of surplus energy can meet the load demand. However that is not the case, for thermal units run on heat may require timely maintenance outages or shutdowns. Moreover, the announced capabilities by some IPPs are not met when required. One such example is Hub Power company, whose installed capability is 1,200MW but could not supply more than 600MW round the clock in recent times. However, now, it is capable enough to supply 900MW as one of its unit recently became operational after a prolonged maintenance process.
At the time when this article was written, Rousch Power with 395MW, Saba Power with 123MW, Habibullah Coastal Power Company (HCPC) with 129MW and Liberty Power with 207MW are on annual maintenance shutdowns, causing a net shortfall of 844MW for a certain time period.
The maintenance outages and capability shortfall is not only the case with IPPs; rather it also exists with Wapda thermal units. These thermal units often trip due to some technical reasons in the network or can avail outages from time to time, causing serious shortfall in generating capabilities. A 500MW amount of energy is also exported to Karachi Electric Supply Company (KESC) during peak hours from Jamshoro’s 220KV grid station, which is in fact a burden on Wapda, especially during peak hours. Moreover, the pipe lines supplying gas to different thermal power units sometimes come under attack by various extremist organizations or gas authorities, causing serious threat to generating capabilities.
Last but not the least, if a nuclear powerhouse trips or avails a shutdown, it needs a long time to restart because of standard routine tests which must be carried out as directed by the nuclear agency. Therefore a nuclear outage means a shortfall of 300MW. This poses a serious threat to NPCC, which is unable to cope with this situation, especially when the generating capability is minimal, while higher authorities strictly instruct “there must be no load-shedding!” Thus they have to come up with “ingenuous” (read half-baked schemes) ways to come up with ways to avoid load-shedding.
Of course, one is forced to consider how load-shedding can be avoided under such circumstances? To understand this idea one must once again, review one of the main functions of NPCC, that is, voltage and frequency control. In Pakistan, a 50Hz frequency system used and for all the appliances connected to Wapda, the frequency must remain ideally stable at 50Hz for optimum efficiency. In technical terms, when would it be 50Hz? Simply put, if the demand and supply of the system becomes equal, the frequency remains stable at 50Hz.
For example, if the energy demand at any given time is 9,000MW and the system is also supplying the same amount, then the frequency will remain at 50Hz and voltage will remain stable. Now let’s suppose that the demand increases to 9,500MW and the system cannot provide more than 9,000MW, then 500MW must be shed to make the system reliable and safe.
Another way is to make the system vulnerable, by supplying 9,000MW to the load demand of 9,500MW. This will cause both the voltage and frequency to drop in the system. The system frequency starts dropping as demand increases and supply remains constant. The frequency may reach a value of 49.4Hz due to the abovementioned factor and hence load-shedding is avoided at the cost of the voltage and frequency of the system. One can relate this to the example of a connected motorshaft running on full load. If the the load is increased on the shaft without providing extra energy to the motor, the shaft and ultimately the whole system will break down.
Low voltages and frequencies result in poor performance of industrial and medical equipment. Another important factor is that almost all generators in the network have under-frequency tripping at 49.20Hz (with little variation) and, therefore, the system is being operated at low frequencies, just to avoid load-shedding, making it extremely dangerous and vulnerable. This means that if the frequency goes beyond the limits of generators, cascaded tripping would start occurring in the integrated system, causing a blackout in the country. Under these circumstances, engineers in the national power control room remain under a great deal of stress to keep eye on the system round the clock.
One feels that new planning activities carried out by the government regarding power sector development, must be co-ordinated and discussed with the higher authorities of NPCC. The people in this organization have a lot of experience and can play an important role in the economic development of the country.
Pakistan is observing almost an 8 per cent rise in load demand per year. With this situation efforts must be made to improve both hydel and thermal generation capabilities. Improving generating capabilities is the only way to get rid of load-shedding in future and attain sustainable economic growth.
The writer
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