ON THE ISSUE OF COMPENSATION OF THE REACTIVE POWER LOADING UNIT OF THE INDUSTRIAL ENTERPRISE
Authors: Khmelnytskyi E. , Klyuyev O. , Shramko Yu. , Dekhtiar K. 
Published: June 2022

This paper solves the practical problem of reactive power (RP) compensation of the load unit of the chemical plant. The peculiarity of this node is the presence of powerful asynchronous motors in the absence of synchronous machines.

The load node is powered by a node substation located on the territory of the enterprise, on a 150 kV transmission line. Two step-down transformers TDNS–1600–150 / 6 kV, power supply load 0,4 kV from two transformers TM-2500–6 / 0.4 kV are installed at the settlement substation.

The total active load of the unit is 12,540 kV, reactive — 7,210 kVAr. Currently, the main source of RP for the node is the power supply system (SPS) and partially generators of its own thermal power plant (TPP) with a capacity of 2–112 MW.

As you know, factory TPP are sources of thermal energy for the technological needs of enterprises with low electricity production, so the possible task of choosing the best source of reactive power.

The situation in the supply of electricity to industrial enterprises of Ukraine is complicated, it is determined by the ever-increasing tariffs for electricity, and is also regulated by the instructions on compensation of RP.

Here it is necessary to note the latest instructions of the Ministry of Energy of Ukraine dated 06.02.2018 № 87 and the NERC supplement dated 28.01.2018, which regulate the procedure for settlements for the generation (consumption) of reactive power by industrial enterprises. A feature of the new methodology is the determination of the economic equivalent of reactive power (EERP), taking into account the cost of active energy.  

Based on the standard power factor (according to the new method tg–0.25), the reactive power from the SPS for the load unit can be obtained in the amount of 3140 kVAr. Uncompensated RP in the amount of 4070 kVAr, and taking into account the increase in load by 5% — 4480 kVAr, it is advisable to compensate at the expense of the own needs RP.

Given the above, the best option to compensate for the RP of the load node are the capacitor banks (BSC) to the lack of synchronous motors to drive the technological mechanisms of the enterprise.

            The classical method of technical and economic calculations for reactive power compensation, set out in the works of F.F. Karpova and L.V. Litvak, provides for the definition of such a parameter as the cost of active power losses, which includes the following components: a — specific costs due to the expansion of SPS to cover losses of main power (UAH / kW) and b — specific costs of electricity generation (approximately equal to the cost of electricity on power plant tires (UAH / kWh)). Determining the values of these components is significantly difficult  to the lack of systematic data on the cost of electricity, especially in the requirements of the Ministry of Energy for the purchase of energy from renewable sources, which may affect the accuracy of some data, but not essential.

According to the calculations: indicator a = 4110 UAH / kW, b = 0,573 UAH / kW and the specific cost of active power losses С0 = 6075 UAH / kW. Then the amount of costs for the transfer of reactive power from the power center to the voltage node will be 109.9 thousand UAH.

Of the two options for installing BSC on the 6 kV or 0.4 kV side, you should choose the option of transmission of RP through step-down transformers TM-2500–6 / 0.4 kV, which is confirmed by the calculations performed (certainly take into account the significant difference in BSC cost of 0.4 kV).

Estimated costs for the installation of BSC on the 6 kV side are: 4´20995 = 83980 UAH, taking into account the cost of the input device and the battery of capacitors with a capacity of 1125 kVAr. For each section of 6 kV busbars, two sections of over-regulated BSC are installed, as with a stable reactive load, if necessary, one section of capacitors can be completely disconnected.

As you can see, a more economical option is to install BSC at the enterprise in the load node, taking into account the SPS requirement for consumption of RP in the hours of minimum active load. In the long run, this technical solution gives a significant economic effect.