If to compare percentage of losses of power in transformers and lines of electricity transmissions, it is possible to note that in transformers it is more than power loss than in power lines.

Profitability to operation of a network is characterized by coefficients of the useful action on power losses ( ) and the electric power ( ):

,

where P1, W1 – value of power and the electric power which is generated by power supply rails.

They are determined by formulas:

The power supply generates capacity:

Р₁ = Р₂ + =15+0,665 = 15,665 МВт,

and electric power:

W₁ = W₂ + = 100500 + 4755,5= 105256 МВт·г.

Coefficients of the useful action make:

- on power

,

- on the electric power

.

The instantaneous ( ) it is more than average ( )

Value of coefficient of technological losses on transportation of the electric power equals:

.

it doesn't exceed normative technological losses, which according to article No. 329 HKPE від 10.03.2011are equated to 5,65%.

Capacities at the beginning and at the end of each line і each transformer, and tension in all nodes to the diagram are given in fig. 6.2

6.3 The analysis of tension on buses of customers

Requirements to quality of the electric power are formulated at GOST 13109-97. More controlled figure of merit is the voltage deviation. The principle of counter regulation is directed on execution of requirements of GOST 13109-97 of a relative deviation of tension.

The voltage level can be considered provided if the condition is executed:

де - where the actual voltage level on buses of 6-10, kV

desirable voltage level according to the principle of counter regulation, kV;

level of regulation of regulation under loading devices, %.

Let's evaluate control range of transformers (tab. 2.10).

Behind table 6.10 Desirable Voltage Level data on buses of customers of Davidovka-35 (T1) it isn't provided in a mode of minimum loads. The reasons of an inadmissible voltage deviation on buses of 6 kV of substations are old and ineffective methods of regulation, the number and quantity of which levels of regulation is insufficient, and besides, is nonrational power supply tension is selected.

According to table 6.10 on tires consumers Davydovka -35 (T1) voltage above the desired voltage. Therefore, in section 3 will need to consider regulating the supply voltage.

Control unit for transformer substation is on the most extreme branch thus provide the desired voltage level in two ways: either reduce the loss of voltage or set control devices with a greater range of adjustment.

Voltage deviation, especially towards its decrease, causing damages in all industries. Also, if you reduce the voltage increases power losses in electric networks. At present in electrical systems used a large number of devices that provide maintenance mode voltage. This is primarily regulated transformers under load transformation ratio, capacitor batteries, static thyristor compensators, synchronous compensators, power generators and more. These devices are equipped with regulators that provide voltage support at some level.

The main means of voltage control in power grids are power transformers with regulation of devices under load and capacitor bank. The feasibility of their application considered in the following sections.

Also check the admissibility of the voltage applied to the primary winding of the transformer. Under Section 35.14 transformers allowed to raise in excess of nominal voltage:

- Long-term - 5% at no higher than nominal and 10% at not higher than 0.25 of the nominal;

- Temporary (up to 6 hours per day), 10% at no higher than nominal.

Test results of which are shown in Table. 6.11, indicating that the voltage supplied to the transformer is acceptable for all stations. Research the supply voltage will be performed in the third chapter of the thesis.

Table 6.10 - Analysis of stress on tires 6 - 10 kV substations consumer

Пара-метри	Name of consumer substations
	Stozhkovo			Davidovka			Gorniak
1		2	3		4	5		7
Тр-р		Т1	Т2		Т1	Т2		Т1
%ст		2,5	2,5		2,5	2,5		2,5
№ст		±2	±2		±2	±2		±2
	mode of the maximum loading
U2ж, кВ		6,3	6,3		6,3	6,3		6,3
U2ф, кВ		6,3	6,26		6,26	6,22		6,26
nотв.ст.		0	0		1	-1		0
U,%		0,0	0,63		0,63	1,27		0,63
	mode of the minimum loading
U2ж, кВ		6,18	6,13		6,1	6,04		5,98
U2ф, кВ		6,11	6,22		6,28	6,07		5,93
nотв.ст.		1	1		2	2		3
U,%		1,13	1,47		2,95	0,50		0,84

Table 6.11 - Check the voltage on the high voltage side of the transformer

Name of substation	№ тр	Type of transformer	UВН кВ	1,05·UВном кВ		U1 кВ	U1 / UВном	Allowable?
Gorniak-110 (T1)	Т1	ТДН-25000/35	36,75	38,59	0,20	36,93	1,00	Yes
	Т2	ТД-10000/35	36,75	38,59	0,15	36,88	1,00	Yes
Stazhkovo-35 (T1)	Т1	ТД-10000/35	36,75	38,59	0,20	36,14	0,98	Yes
	Т2	ТД-15000/35	38	39,90	0,19	36,14	0,95	Yes
Davydovka-35 (T1)	Т1	ТД-15000/35	36,75	38,59	0,27	35,47	0,97	Yes