100
SIVACON S8 Planning Principles – Technical annex
Rated power
S
rT
Rated voltage
400 V AC / 50 Hz 525 V AC / 50 Hz 690 V AC / 50 Hz
Rated value of the short-
circuit voltage u
kr
Rated value of the short-
circuit voltage u
kr
Rated value of the short-
circuit voltage u
kr
4 % 6 % 4 % 6 % 4 % 6 %
Rated
current I
r
Initial short-circuit
alternating current I
k
“
1)
Rated
current I
r
Initial short-circuit
alternating current I
k
“
1)
Rated
current I
r
Initial short-circuit
alternating current I
k
“
1)
50 kVA
72 A 1,933 A 1,306 A 55 A 1,473 A 995 A 42 A 1,116 A 754 A
100 kVA
144 A 3,871 A 2,612 A 110 A 2,950 A 1,990 A 84 A 2,235 A 1,508 A
160 kVA
230 A 6,209 A 4,192 A 176 A 4,731 A 3,194 A 133 A 3,585 A 2,420 A
200 kVA
288 A 7,749 A 5,239 A 220 A 5,904 A 3,992 A 167 A 4,474 A 3,025 A
250 kVA
360 A 9,716 A 6,552 A 275 A 7,402 A 4,992 A 209 A 5,609 A 3,783 A
315 kVA
455 A 12,247 A 8,259 A 346 A 9,331 A 6,292 A 262 A 7,071 A 4,768 A
400 kVA
578 A 15,506 A 10,492 A 440 A 11,814 A 7,994 A 335 A 8,953 A 6,058 A
500 kVA
722 A 19,438 A 13,078 A 550 A 14,810 A 9,964 A 418 A 11,223 A 7,581 A
630 kVA
910 A 24,503 A 16,193 A 693 A 18,669 A 12,338 A 525 A 14,147 A 9,349 A
800 kVA
1,154 A - 20,992 A 880 A - 15,994 A 670 A - 12,120 A
1,000 kVA
1,444 A - 26,224 A 1,100 A - 19,980 A 836 A - 15,140 A
1,250 kVA
1,805 A - 32,791 A 1,375 A - 24,984 A 1,046 A - 18,932 A
1,600 kVA
2,310 A - 41,857 A 1,760 A - 31,891 A 1,330 A - 24,265 A
2,000 kVA
2,887 A - 52,511 A 2,200 A - 40,008 A 1,674 A - 30,317 A
2,500 kVA
3,608 A - 65,547 A 2,749 A - 49,941 A 2,090 A - 37,844 A
3,150 kVA
4,550 A - 82,656 A 3,470 A - 62,976 A 2,640 A - 47,722 A
1)
I
k
“ uninfluenced initial symmetrical transformer short-circuit current in consideration of the voltage and correction factor of the transformer impedance in
accordance with IEC 60909-0, without considering the system source impedance
Tab. 10/6: Rated currents and initial symmetrical short-circuit currents of three-phase distribution transformers
Exemplified by
• Rated transformer power S
rT
= 500 kVA
• Voltage factor k
k = 1.45 A/kVA for a rated voltage of 400 V
k = 1.1 A/kVA for a rated voltage of 525 V
k = 0.84 A/kVA for a rated voltage of 690 V
• Rated short-circuit voltage u
kr
=4 %
there are the following approximations for U
r
= 400 V:
I
r
= (1.45 x 500) A = 725 A
I
k
“ = (725 x 100 / 4) A = 18.125 kA
10.6 Three-phase distribution
transformers
Important parameters for the connection of the SIVACON
S8 low-voltage switchboard to three-phase distribution
transformers are listed in Tab. 10/6.
Approximation formulas for current estimation, if there are
no specified table values:
For the rated transformer current by approximation:
I
r
= k x S
rT
For the initial symmetrical transformer short-circuit current
by approximation:
I
k
“ = I
r
/ u
kr
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