2 Initial data

Таble 1

Initial data
Type of fuel	The number and power generator, MW	Quantity and power lines load on the generator voltage, MW	Consumption for own need in %	RUSN nominal voltage, kV	The number of lines and the power loads RUSN, MW	Continuation of loads, winter-summer	Nominal voltage of lines to the system, kV	Number of lines and their length, km
Fuel oil	5/63	15/6	7	35	2/45	160/205	110	2/90

Selected turbogenerator from CGW №1

Table 1 - Main technical characteristics

Type of turbogenerator		ТВФ-9-2У	ТВС-81У
Nominal rot. frequency, rpm		3000	3000
Nominal power	Full, МV·А	76,45	40
	Active, MW	54	35
Nom. voltage, kV		8,3	8,3
cosφном		0,9	0,9
Nominal current, kA		6,89	4,11

Selected transformers from CGW №2:

1 transformer of type TRDNC-40000/35 and 1 transformer TDTN-80000/110;

Table 3- Basic technical data of transformers

Transformer type		TRNDS-40000/35	TDTN-80000/110
Rated power, MVA		40	80
Winding voltage, kV	36,75	115	110
	-	38,5	-
	10,5	11	10.5
Losses, kW	36	64	34
	170	365	170
uk, %	-	10,5	-
	12,7	17,5	15
	40	6,5	-

3 Short-circuit currents calculation

We will calculate in relative units. Determine the resistance of the circuit at the base power S_b=1000 МVA

Resistance of generators G1, G2:

Resistance of generator G3:

Define the EMF of the generator G1, G2 and G3:

where I₀=1; U₀=1; cosφ₀=0,85; sinφ₀=0,53.

Resistance of transformer Т3:

Resistance of transformers Т1, Т2:

The resistance of the double-circuit power line:

where - the resistivity of the line is assumed to be equal to 0,4 Om/km.

Figure 2 - The replacement scheme of the CHPP

Simplification of the substitution scheme:

Figure 3— Simplified scheme

Figure 4 - Simplified scheme for the replacement of CHPPs

The initial value of the periodic component of the SC current

where and - the resulting resistance of the circuit branch and the base current.

Three-phase SC current from generator G1, G2 :

From G3:

From system:

Total SC current :

Determination of shock current of SC:

where k_s = 1,94 for generator ТVS-32U3.