Load Management, Load Switching, Load Shedding, Peak Load Tariff

Load management

As mentioned before in the earlier articles, the process of generation-consumption of electricity is a dynamic one. This means that electrical power must be generated continuously as it is being consumed by the users as it is uneconomical and ineffective to store electrical energy in bulk amount.

As the demand for electrical power i.e. electrical load on the system increases, the generators on the power plants may be heavily loaded which increases the overall stress on the power plants of the system. So as the power plants approach their maximum generating capacity, it is absolutely necessary to find other sources of additional power to prevent the system from an eminent breakdown.

Load management, which is also known as Demand Side Management (DSM), is defined as the process of balancing the supply of electrical power in a power system network according to the load or power demand by adjusting the load instead of the power output of power plants. It consists of a set of intellectual or consciously designed activities that are designed to control the power demand from the consumer end. This helps in the reduction of stress on power plants during the peak load periods.

Load management can be directly achieved by cutting off the power supply to the consumers in a scheduled fashion. For that purpose, frequency sensitive relays, time clocks or some special forms of tariffs such as off-peak tariff can be used.

Actually, load management is mainly concerned with the activities which deal with the pattern of energy consumption and its conservation. Power utilities can benefit from load management as long as the load in peak period is reduced and shifted to the off-peak periods. Since it involved interruption of power supply, it must have an acceptable level of convenience to the consumers and they must obtain some form of benefit from load management such as reduction in tariff rate.

Some of the load management strategies commonly used are described briefly below.

• Differential tariff:

In this method, the electricity consumption pattern of the consumers is influenced by imposing different rates of tariffs at different periods of a day. The rate for electrical power can be set high during peak periods and can be set low during off-peak periods. By doing so, the consumers are encouraged to utilize electrical energy during off-peak periods.

• Load staggering

Load staggering is the process in which the work hours of industries or business ventures are shifted by sometime to decrease the peak demand. The feeders can be switched on/off by the field staffs manually for this purpose.

• Interruptible power supplies

In this method, the power supplies to the high energy demanding loads or electrical appliances are cut off to reduce the demand during peak periods. Consumers using electric appliances and equipment that demand high electrical power should be governed by some contract that subjects them to interruption of power supply during peak hours.

Some of the advantages of load management are as follows:

1. Many load management strategies and activities have been and can be introduced in order to reduce the cost of meeting energy demand.
2. With the introduction of new energy efficient technologies and strategies, the need for running peaking power plants can be reduced. These peaking power plants may emit harmful gasses to the environment.
3. By introducing proper load management strategies, the need for construction of new power plants can be postponed.
4. The cost of generation per unit is lowered.
5. The reliability of the system is improved as the number of blackouts or unexpected power outages are reduced.
6. The stress on the power plants is reduced significantly which reduces the local air pollution due to decreased emission of harmful gasses to the environment.
7. The need for importing fuel is reduced as the power demand on the system decreases.
8. Due to lesser cost of generation per unit, the consumer's electricity bill is also reduced.

Load switching

Load switching is the process of disconnecting loads that consume a large amount of electric powers such as air conditioner units or electric water heaters from the supply during peak load periods. The process employs a load control switch for connecting/disconnecting the loads. It is a remotely controlled relay which is placed on appliances that consume a large amount of electric power.

Load switches are a one-way switch which receives the command signals to open from the power companies or utilities. They consist of a communication module and a relay and can be used as an integral part of a smart grid.

The process of load switching is called on-load switching if the load switch can be operated while the load is still operating or while some amount of current is passing through the switch. Conversely, the process is known as off-loading switching if the switch is to be operated if there is no current passing through it.

Load shedding

Load shedding is a process of shutting down a part or multiple parts of the distribution system which is practiced by electric utilities to prevent the breakdown of the system when the power demand is excessively high and cannot be met with current generation capacity.

Load shedding is a common situation in under-developed countries like Nepal where the demand for electric power exceeds the generation capacity. The current generation capacity of Nepal is approximately 770 MW. This is the maximum generation obtained in the monsoon season. The production of Nepal drops down to approximately 1/3rd of the installed capacity during the dry season. The demand for electric power in the current scenario is approximately 1100 MW (1094.62 MW in November 12, 2012). Thus, it is easily seen that the hydropower capacity of Nepal is seriously underdeveloped compared to its technically feasible potential of 42,000 MW and is overshadowed by the ever increasing demand for energy. Depending upon power import from India, Nepalese citizens may experience load shedding as much as 18 hours per day.

Peak load tariff

Peak load tariff is different from the normal or off-peak tariff to encourage the consumers to utilize electrical energy during off-peak periods. This reduces the total demand in peak periods thereby reducing the overall stress on the system.

The concept of Time of Day tariff has a significant impact on modeling the consumption pattern of the consumers. If different charges are applied for consuming a unit of electricity at different times of a day, the consumers are encouraged to use their equipment during off-peak periods.

An example of ToD tariff is shown in the table below. The table illustrates the ToD tariff structure of NEA. Additional information regarding the tariff structure can be found in the authority's official websitehttp://www.nea.org.np/and the students are also advised to go through the proposed tariff structure of BPC in 2013 which can be found in this linkhttp://www.doed.gov.np/notices/BPC-Tariff-Proposal-2013.pdf.

The students will also study about Demand Side Management in their course of Utilization of Electrical Energy and will, therefore, gain a better understanding after consulting their subject teachers of the respective subject.

References

Wikipedia. (2016).Load Management.Retrieved fromhttps://en.wikipedia.org/

The ToD tariff rate of NEA was taken from the handbook provided by my subject teacher Mr. Gopal Joshi Subedi.