Empirical methods for calculating electrical loads
Purpose of empirical methods for calculating electrical loads
The lack of information on individual energy consumers in some cases led to the need to develop empirical calculation methods, which include: the demand factor method, the method of specific electricity consumption per unit of production, the method of specific load density per unit of production ■ area.
Empirical methods are based on information about load energy consumption modes in the form of various coefficients and indicators (Ks, Sud, pud). These methods are simpler, but the accuracy of their calculation depends on the analogy of the technological process and equipment of the newly designed user with the technological process and equipment of the user, for which the values of Kc, Sud, pud are recommended in the reference literature are obtained.
Search coefficient method
The basic calculation formula is as follows: Rr = Ks • Rust; Qр = Пр × tgφ,
where Rust is the total installed power of the user's electrical receivers; Ks — demand factor of user installed capacity; tgφ — reactive power factor of the consumer.
The values of Kc and tgφ for different users are given in the reference books. This method can be used to determine the design loads of workshops and the enterprise as a whole.
Method of specific electricity consumption per unit of production
Using this method, it is possible to determine only the average load for a certain time interval (hour, shift, day, month, quarter, year). The expression calculated by this method has the form: Рср = Суд • P / T,
where P is the production volume for the time interval T; Court - specific energy consumption for the production of products.
Court values for a number of electrical receivers of workshops and enterprises are given in the reference literature.
The method of specific load density per unit of production area
The specific load density is determined on the basis of a study of the loads of workshops of operating industrial enterprises:
sud = Smax / Fc,
where Smax is the maximum total shop load as determined by active and reactive energy meter readings taken after 0.5 hours during the busiest shift period; kV × A; Fc — production area of the workshop, m2.
This calculation method was proposed by Prof. Yu.L. Mukoseev for designing workshops with frequently changing technological processes (mechanical, assembly, weaving, etc.). Knowing the area of the workshop planned by the project and the values of ssp observed in similar operating enterprises, it is possible to determine the estimated load of the workshop using the expression: Sр = ssp • Fц.
This method is widely used to determine the design loads of electric lighting receivers:
Rr.o = ore • Fts • Ks.o,
where ore is the specific lighting density, kW / m2; Ks.o — lighting demand factor.