Auxiliary supply and station service

The AC and DC auxiliary systems of the substation: load list, transformer, generator, battery, chargers and switchgear ratings. The schematic and the report are sample documents.

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Capabilities

Auxiliary calculations and documents

The design builds the load list from the substation, and you can edit it. The sizes follow from the maximum demand and the DC duty cycle.

AC system

Load list with duty factors and maximum demand
Transformer sizing
Generator sizing and motor-start dip
Breaker ratings per standards set, below

DC system and documents

DC duty cycle per IEEE 485 §5
Battery sizing per IEEE 485 §6
Charger sizing per IEEE 946
LT / DC or station service schematic in DXF and PDF
Calculation report in PDF

Standards sets

AC and DC systems per standards set

The voltages, the switchgear and the generator follow the standards set of the project.

Item	IEC, CEA and CBIP	ANSI, IEEE and NESC
AC	IEC, CEA and CBIP415 V, ACB and MCCB ratings per IEC 60947-2	ANSI, IEEE and NESC480Y/277 V, breaker frames per IEEE C37.13-2015 §5.4
Generator	IEC, CEA and CBIPDG set, motor-start dip per ISO 8528-5 (class G3)	ANSI, IEEE and NESCStandby generator with an automatic transfer switch, motor-start dip
DC	IEC, CEA and CBIP220 V DC, battery per IEEE 485-2020, chargers per IEEE 946-2020	ANSI, IEEE and NESC125 V DC, vented lead-calcium, 8 h duty, battery per IEEE 485-2020, chargers per IEEE 946-2020

Sample project

Results, 220/33 kV pooling substation

The motor-start dip is within its limit. Sample design per IEC, CEA and CBIP.

Connected load: 248.4 kW
Maximum demand: 133.0 kW, 152.2 kVA
Auxiliary transformers: 2 × 250 kVA
DG set: 250 kVA
Motor-start dip: 14.8 %
Battery sets: 2
Chargers: 2

Calculation trail

Equation, input values, result and clause per step

The calculation trail shows how the design reaches its sizes, from the maximum demand to the switchgear ratings.

1Maximum demandDesign rule
$P = \sum q_{i} P_{i} d_{i}, Q = \sum P_{i} tan (arccos pf_{i}), S = P^{2} + Q^{2}$
25 loads, connected 248.4 kWP = 133.0 kW, Q = 74.0 kvar, S = 152.2 kVA
2Auxiliary transformerDesign rule
$S_{TR} = 1.2 S$
required 182.7 kVA2 × 250 kVA (one duty, one standby)
3DC duty cycleIEEE 485 §5
$I (t) = I_{cont} + I_{light} (t) + I_{trip} (t) + I_{close} (t)$
4 periods, 107 cells at 240.8 V floatcontinuous 10.5 A
4Cell sizing sectionsIEEE 485 §6.3
$F_{S} = \sum (A_{p} - A_{p - 1}) K_{t}$
4 sectionslargest section 118.8 Ah
5Battery capacityIEEE 485 §6.4
$C = F_{S} k_{aging} k_{margin} k_{temp}$
required 163.4 Ah2 × 200 Ah C10
6ChargersIEEE 946
$I = L + \frac{1.1 C}{H}$
L 10.5 A, C 200 Ah2 × 40 A float-cum-boost, 11.6 kW each
7DG set and motor-start dipISO 8528-5 (class G3)
$S_{DG} = 1.2 max (S, P /0.8), Δ U = \frac{S _{start}}{S _{start} + S _{DG} / x _{d}^{''}} \leq 15%$
required 199.5 kVA, largest motor Electric fire-water pump (main) 37 kW250 kVA, dip 14.8 %
8Switchgear ratingsIEC 60947-2, IEC 60269-1, IEC 61439-2
$I = \frac{S}{3 U}, I_{n} \geq I$
18 devices at 415 V and 220 V DCACDB 630 A, DCDB 315 A

Document

Auxiliary supply calculation report

The report states the load list, the transformer, the DG set, the battery, the chargers and the assumptions.

Auxiliary supply calculation reportSSL-C-AUX-001 · Rev 0 · 3 pages · PDF · 78 KB

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