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Appendix 1: AC Modern Equivalent Assets and Replacement Costs


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Appendix 1: AC Modern Equivalent Assets and Replacement
Costs


1.1
Detailed Design Assumptions

1.1.1
Assumptions Common to Generic Substation Building Blocks

Sizes of substations are categorised as follows:

Category
No. of HV
bays
Major 14
Medium 8
Small 6
Rural 2

It was assumed that there were to be no gantries and all busbars were to be of
rigid tubular aluminium. Worse case dimensions have been applied, e.g.
33kV as opposed to 11 kV switchgear was used to dimension the switchgear
room. All assumptions and design parameters are based on best practice
principles as if the project was to be built today. Designs are based on
Transpowers current practice.

1.1.2 Building Blocks for AC Substations - Buildings

Generic Buildings Building Blocks Identified

A suitable Building building block was designed for each of the following
substation types:

1. Major
outdoor,
2. Major
indoor,
3. Medium
outdoor,
4. Small
outdoor,
5. Rural outdoor, and
6. Rural
indoor.

Specific Buildings Building Blocks Identified

Due to the specific nature of the buildings, the Building costs for the following
stations were assessed individually.

1. Tiwai
2. Motunui

Generic Buildings: Key Assumptions

No amenities are provided for in the building layout, i.e. no mess room, toilets,
or other work space.

The control room is a metal clad timber framed structure, while the switchgear
room has concrete-filled block-work walls. Concrete slabs on grade are used


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with a false floor using Uni-Strut supports in the control room for panel fixing
and cable entry.

Switchgear room sizes have been based on the use of 33kV switchgear with
dimensions of 1m wide and 2.35m deep. Total switchgear length was based
on the panel widths given in Table A1.1.

Table A1.1: Panel Widths
Panel Type
Panel
width (m)
Feeder 1
Incomer 1
Bus Section
1
VT per Bus
1
Busbar connection
1

The control room size is based on:
All panels 600 x 600 x 2200mm high, with 1200mm clearance, front and
rear, of all panels 3 x 33 kV circuits per protection panel 2 x 110 kV line circuits per protection panel 1 x 220 kV line circuit per protection panel (Prot 1 & Prot 2) 1 x transformer bank per protection 2 x protection signalling equipment per 220 kV line 1 x protection signalling equipment per 110 or 66 kV line 10 x protection signalling equipment per panel 12 panels per row No 24 V d.c. system (communications asset)

Unique Buildings: Key Assumptions

The cost estimates have been based on detailed design drawings available in
Transpowers document system. Grades of materials and building services
performance levels have been assumed to be average and typical of a standard
type of switchgear building. Generally the cost estimates for the building
structures include sub-floor cable ducts and normal building services. External
and internal finishes such as painted surfaces have been based on
assumptions and may not reflect actual finish.

1.1.3 Building Blocks for AC Substations - Power Transformers

Power Transformers Building Blocks Identified

The transformer building blocks chosen are given in Table A1.12.

BB No. = building block reference
HV
= nominal Voltage of High Voltage winding
ID =
indoor
LV
= nominal Voltage of Low Voltage winding
TV/mva
= nominal Voltage of Tertiary winding / maximum three
phase continuous rating of tertiary winding
TY
= vector group, as follows:


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A
= auto-transformer
D-S
= delta-star
S-S
= star-star
S-D
= star-delta
PH
= number of phases per unit

m
= metres distance from centre bank to protection cabinet
MVA = maximum three phase continuous rating of high and low voltage
winding
NCT = neutral current transformer
OT
= On-load tap-changer fitted.

Transformer Infrastructure and Auxiliaries Building Blocks

Transformer infrastructure building blocks were identified as detailed in Table
A1.2.

Table A1.2: Transformer Infrastructure Building Blocks
No. Description
1
Transformer Infrastructure I (3 phase - 30 m)
2
Transformer Infrastructure II (3 phase - 60 m)
3
Transformer Infrastructure III (3 x 1 phase 60 m)
4
Transformer Infrastructure IV (3 x 1 phase 120 m)
5
Interconnecting bank structure 3 phase
6
Interconnecting bank structure 1 phase (spare)
7
11 kV Cable for Stn Serv Transf
8
22 kV Cable for Stn Serv Transf
9
33 kV Cable for Stn Serv Transf
10 11/0.4 kV, 50 kVA Station services transformer
11 22/0.4 kV, 50 kVA Station services transformer
12 33/0.4 kV, 50 kVA Station services transformer
13 11 kV Earthing transformer
14 22 kV Earthing transformer
15 33 kV Earthing transformer
16 11 kV Zig Zag Earthing Transformer
17 22 kV Zig Zag Earthing Transformer
18 33 kV Zig Zag Earthing Transformer
19 11 kV Surge Arrester (ID)
20 22 kV Surge Arrester (ID)
21 33 kV Surge Arrester (ID)
22 50 kV Surge Arrester
23 66 kV Surge Arrester
24 110 kV Surge Arrester
25 220 kV Surge Arrester
26 11 kV Cable, 5 MVA
27 11 kV Cable, 7.5 MVA
28 11 kV Cable, 10 MVA
29 11 kV Cable, 15 MVA
30 11 kV Cable, 20 MVA
31 11 kV Cable, 30 MVA
32 11 kV Cable, 45 MVA
33 11 kV Cable, 60 MVA


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Table A1.2: Transformer Infrastructure Building Blocks
No. Description
34 11 kV Cable, 100 MVA
35 22 kV Cable, 30 MVA
36 22 kV Cable, 50 MVA
37 33 kV Cable, 25 MVA
38 33 kV 10 MVA
39 33 kV 15 MVA
40 33 kV 20 MVA
41 33 kV Cable, 30 MVA
42 33 kV Cable, 50 MVA
43 33 kV Cable, 60 MVA
44 33 kV Cable, 100 MVA
45 33 kV Cable, 120 MVA
46 33 kV Cable, 200 MVA
47 11 kV Cable termination structure
48 22 kV Cable termination structure
49 33 kV Cable termination structure
50 11 kV Structure for delta bus
51 22 kV Structure for delta bus
52 33 kV Structure for delta bus
53 66 kV Structure for delta bus
54 110 kV Structure for delta bus
55 NCT
56 11 kV NCT standard
57 Two winding transformer protection
58 Three winding transformer protection
59 Residual voltage protection
60 Protection, point on wave switching relay
61 220 kV, 6000 A, 2 ohm neutral earthing resistor
62 220 kV, 3000 A, 2 ohm neutral earthing resistor
63 220 kV, 1500 A, 2 ohm neutral earthing resistor
64 220 kV, 750 A, 2 ohm neutral earthing resistor
65 66 kV, 84 ohm neutral earthing resistor
66 66 kV, 168 ohm neutral earthing resistor
67 33 kV, 42 ohm neutral earthing resistor
68 33 kV, 84 ohm neutral earthing resistor
69 22 kV, 28 ohm neutral earthing resistor
70 22 kV, 56 ohm neutral earthing resistor
71 11 kV, 14 ohm neutral earthing resistor
72 11 kV, 28 ohm neutral earthing resistor
73 20 MVA power transformer sound enclosure
74 40 MVA power transformer sound enclosure
75 80 MVA power transformer sound enclosure
76 160 MVA power transformer sound enclosure

Power Transformers: Key Assumptions

Distribution (two winding) transformers are equipped with protection having
the following characteristics:


81 Differential protection. The valuation assumes a digital relay that does not
need interposing current transformers. This relay provides trip circuit
supervision for one set of trip coils. No test switches or other testing facilities are assumed except for shoring
of the current transformer connections when the relay is removed from the
case. It is assured that the feeder protections will cover the transformer
while the transformer protection relay is being tested. Circuit breaker control push buttons are on connection circuit protections. MVAJ26 relay used for protection 1 (Buch) MVAJ26 trips into the same coils as the feeder (incomer) protections.
They provide trip circuit supervision.

Interconnecting banks are equipped with protection essentially the same as for
distribution transformer protection, with the following enhancements:
Three winding transformer protection relay Residual voltage protection on the tertiary circuit. Under impedance protection on the 110 kV and 66 kV circuits.