Reserve  capacity  of  power  stations, spinning  and  maintenance resaves

 

In electricity networks, the operating reserve is the generating capacity available to the system operator within a short interval of time to meet demand in case a generator goes down or there is another disruption to the supply. Most power systems are designed so that, under normal conditions, the operating reserve is always at least the capacity of the largest generator plus a fraction of the peak load.

The operating reserve is made up of the spinning reserve as well as the non-spinning or supplemental reserve:

The spinning reserve is the extra generating capacity that is available by increasing the power output of generators that are already connected to the power system. For most generators, this increase in power output is achieved by increasing the torque applied to the turbine's rotor.

Spinning Reserve is the on-line reserve capacity that is synchronized to the grid system and ready to meet electric demand within 10 minutes of a dispatch instruction by the ISO. Spinning Reserve is needed to maintain system frequency stability during emergency operating conditions and unforeseen load swings.

The non-spinning reserve or supplemental reserve is the extra generating capacity that is not currently connected to the system but can be brought online after a short delay. In isolated power systems, this typically equates to the power available from fast-start generators.[3] However, in interconnected power systems, this may include the power available on short notice by importing power from other systems or retracting power that is currently being exported to other systems.

Non-Spinning Reserve is off-line generation capacity that can be ramped to capacity and synchronized to the grid within 10 minutes of a dispatch instruction by the ISO, and that is capable of maintaining that output for at least two hours. Non-Spinning Reserve is needed to maintain system frequency stability during emergency conditions.

Generators that intend to provide either spinning and non-spinning reserve should be able to reach their promised capacity within roughly ten minutes. Most power system guidelines require a significant fraction of their operating reserve to come from spinning reserve.[3] This is because the spinning reserve is slightly more reliable (it doesn't suffer from start-up issues) and can respond immediately whereas with non-spinning reserve generators there is a delay as the generator starts-up offline.

Non-Spinning Reserve is off-line generation capacity that can be ramped to capacity and synchronized to the grid within 10 minutes of a dispatch instruction by the ISO, and that is capable of maintaining that output for at least two hours. Non-Spinning Reserve is needed to maintain system frequency stability during emergency conditions.

 

Cold reserve is ensured by special reserve units with small start-up and spin-up time. Period of the cold reserve start-up is deemed to be from 2 to 24 hours and more. Cold reserve in a power system is that reserve capacity which is available for service but normally not ready for immediate loading. Eg We have an idle generator that can be pressed into service if demand increases.

Hot reserve in a power system is that reserve capacity which can be made available quickly. For example we have a hydroelectric generator of rating say 100MVA but currently supplies only 70MVA. In this case we have 30MVA hot reserve than can be loaded immediately by simply opening the valve to the hydro turbine.

Under the power-on reserve we mean reserve capacity of currently operating units that can be used immediately (started-up in minutes). A power-on reserve includes:

- A spinning reserve is an operating reserve of the system that is placed on the operating underloaded units of power plants;

- A fast start-up reserve is an operating reserve of the system that is placed on the fast start-up units whose full loading time does not exceed the time of spinning reserve start-up.

- A standing reserve is capacity of idle properly operating units of power plants within the energy system. A standing reserve equals to difference between operating and power-on capacity of the power system. Standing reserve includes:

- A hot reserve of the system is an operating reserve located at TPP units where a boiler is in hot reserve.

- A cold reserve of the system is an operating reserve located at TPP units where boilers are in cold reserve.

It should be mentioned that a hot reserve of the system also includes an operating reserve located at TPP with transverse relations where the boiler is maintained in the hot state, and the

turbine generator is shutdown. When the boiler is immobilized for a hot reserve, the specified steam pressure and temperature are maintained in it.

A power-on reserve is started-up into minutes, whereas activation of a standing reserve requires 1-2 hours and more.