Clarification Lot C Technical List No.03 Sr. Ref Clause ... · PDF fileClarification Lot C...

Employer : The Kenya Electricity Transmission Company Ltd 10.08.2015

Invitation to Bid No KETRACO/PT/010A,B&C/2015 – Lot A,B&C

Sr.

No.Ref Clause / Page Description Bidders Query KETRACO response

1 Lot C Nairobi East LVAC and DC - for the purpose of the tender the bidders

shall offer a new system covering the 400kV and 220kV.

Control System - the price schedule is clear, therefore

please offer as required.

2 1. Extension of HB1 and HB2 busbars are not in the

scope.

2. For the purpose of the tender bidders shall assume

Lamu construction (under the Power Plant scope) will

commence first prior to Lot C works.

3. Under this tender the bidders shall provide a new SCS

system for the entire substation

3 1. Garsen feeder is not in the scope, so please focus on

the required scope only.

2. Please focus on the required scope only.

3. No, please follow as required in the tender drawings

4. Revised SLD is uploaded in KETRACO website as

Addendum 03.

5. Available existing drawings are uploaded in KETRACO

website as Addendum 03.

6. Revised Layout is uploaded in KETRACO website as

Addendum 03.

7. Available existing drawings are uploaded in KETRACO

website as Addendum 03.

Design, Manufacture, test, Supply and Installation of 400 kV TRANSMISSION PROJECT

Clarification Lot C Technical List No.03

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4 1. The technical specification is not a site specific

document and therefore site specific requirements are

detailed in the technical schedules.

2. For Lamu and Hindi the altitute shall be below 1000 m

3. (a) The specification is clear.

(b) Neutral Reactor is required.

(c) Please comply as required.

(d) Yes, correct.

(e) Refer to TAC 2 item no. 12.

5 TAC 1 Lamu It was stated as:

Lamu is not constructed,

therefore for tendering pupose

bidders may assume SCS is

installed.

Bidders shall offer for a new SCS as stated in item 2

under this TAC.

6 Clarification Lot

C Technical

List No.01

Q.No 35

There are discrepancies in the

dimensions of the plot area.

The plot co-ordinates received

from site visit for Nairobi East

substation has the dimension of

850 x 300 m .

As per pre-bid clarification reply it

is 1500 x 300m.

Please clarify which is right.

Please follow the diamensions provided in the

calrifications.

7 General Substation fencing/levelling shall

be done only for the area

required for substation platform

area including future feeders (as

per Specification) and not for the

complete 1500x300 m plot. No

scope of works like

fencing/levelling/landscaping/bus

h clearing is envisaged in the

unused/free area. Please

confirm.

Correct. No levelling, clearing, landscaping works

required outside substation fencing which are not used.

However boundary fencing would be required to cover the

whole land plot. Refer to bid drawings.

8 General Existing 220kV towers are meant

for LILO to Koma rock substation

as understood from site visit.

There is no scope of works

envisaged for the same. Please

confirm.

The LILO is under OHL Lot A work package.

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9 General Please inform us the source and

destination substations

connected by the transmission

line towers located on the road

between Koma Rock and Nairobi

East substation for information.

Refer to bid drawings.

10 Clarification Lot

C Technical

List No.01

Q.No 60

Please clarify whether the neutral

earthing resistor rating shall be

1050 A for 30 sec or 500 A for 10

sec.

1050A for 10 secs. (Supersedes item no. 60 TAC 1)

11 General Please provide the plot co-

ordinates of Koma Rock

substation.

Please read TAC 1 and 2.


C Technical

List No.01

Q.No 55

As per clarification reply ,

Minimum capacity of tertiary

winding shall be 1/3 of main

winding capacity.

Hence, Main winding 3 ph

Capacity (Full cooling) - 300 MVA

Tertiary winding 3 ph capacity -

300/3 - 100 MVA

External loading - 0.5 MVA

Total capacity of tertiary winding

3 ph - 100.5 MVA

But as per transformer datasheet

, 70 MVA is given.

Please clarify final rating required

and update the datasheet.

Please read TAC 1 and 2.

13 General As the external loading of the

tertiary winding is 500 kVA , we

presume transformer tertiary

bushing shall be rated for the

same. Please confirm.

Please comply to IEC standard.

14 Remote end

scope of works -

Protection and

telecommunicat

ion

&

Clarification Lot

C Technical

List No.01

Sr.NO : 79

Nairobi East to 400kV Lamu -

1&2

(i)We presume that make and

type of 87L line Differential relay

at Nairobi East to 400kV Lamu -

1&2 lines can be assumed by the

contractor.

(ii)87L at Lamu SS shall be

matched by other end

contractor based on 87L relay at

Nairobi East SS.

Please confirm.

Please read TAC 1.

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15 Remote end

scope of works -

Protection and

telecommunicat

ion

&

Clarification Lot

C Technical

List No.01

Sr.NO : 79

Nairobi East to 400kV Isniya -

1&2


type of 87L line differential relay

at Nairobi East to 400kV Isinya -

1&2 lines can be assumed by the

contractor.

(ii)87L at Isinya SS shall be



Nairobi East SS.

Please confirm.

Please read TAC 1.

16 Remote end

scope of works -

Protection and

telecommunicat

ion

&

Clarification Lot

C Technical

List No.01

Sr.NO : 79

Nairobi East to 220kV

Embakasi


type of 87L line differential relay

at Nairobi East to 220kV

Embakasi line can be assumed

by the contractor.

(ii)87L at Embakasi SS shall be



Nairobi East SS.

Please confirm.

Please read TAC 1.

17 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

Specification :

Volume 2 of 2 ,

page 2 of 385 .

(Price schedule

item no. 2.17 &

4.6)

As per Specification page 2 of

385 "The new 220kV busbars

shall be joined to the existing

Koma Rock 220kV (owned by

KETRACO) busbars to form one

continuous 220kV busbar" .

Hence we presume that no

equipments (Disconnector, Earth

Switch, Circuit Breaker , CT) is to

be considered as a part of Bus

Interconnection at Nairobi East

end as per Lot-C Scope of

works.

Please refer to bid drawings and price schedules.

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18 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

(Price schedule

item no. 2.17 &

4.6)

As per Specification page 2 of

385 "The new 220kV busbars

shall be joined to the existing

Koma Rock 220kV (owned by

KETRACO) busbars to form one

continuous 220kV busbar" .

Hence we presume that no

equipments (Disconnector, Earth

Switch, Circuit Breaker , CT) is to

be considered as a part of Bus

Interconnection at Koma rock end

as per Lot-C Scope of works.

Repeated question as 17.

19 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

(Price schedule

item no. 2.17 &

4.6)

Please provide 220kV

conceptional Busbar philosophy

required at Nairobi East SS end,

after the Busbar interconnections

between Nairobi East SS &

Komarock SS,.

Under this tender the bidders shall provide price for a new

busbar protection system covering:

a. Diameter 3 and 4 (under this scope)

b. Diameter 1 and 2 (constructed by others)

The scope shall include:

a. retrofittings of hardwares/relays into existing panels (of

Diameter 1 and 2) supplied by others.

b. multicore cables from bay marshalling kiosk to busbar

protection panel.

The 220kV Busbar Protection system supplied under this

tender shall be installed in Koma Rock 220/66kV

substation building/room constructed by others. Please

read the specifications for the philosophy required.

20 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

(Price schedule

item no. 4.6)

CT parameters (core details, VA)

at Komarock SS (for providing

220kV Low Impedance & High

Impedance Busbar protection) is

required.

Please furnish the same.

Will be furnished upon contract award.

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21 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

(Price schedule

item no. 2.17 &

4.6)

Please provide approved Bus-

protection configuration -

Centralised or decentralised at

Koma Rock SS End for : Low

Impedance Bus Bar Protection

See item 19.

22 Non-Clarity in

the Limit of

Scope of

"Extension of

220kV Busbar

Protection

System - Low

Impedance &

High

Impedance at

Komorock

Substation"

(Price schedule

item no. 2.17 &

4.6)

We presume that Cable trench ,

power cable, control cables, FO

cables between Nairobi East SS

& Komarock SS is not part of Lot-

C Scope of works.

All works required for the 400kV and the newly extended

220kV shall be part of the scope.

23 General Please provide Scope matrix

between Lot C Scope of works &

Komarock SS - for 220kV Busbar

Extension.

Bidders shall provide this as part of the offer.

24 Nairobi East

SS Section J,

page 171 /

Lamu 400kV

Extn Section J,

page 170),

“As per Technical data sheets of

Power transformer (Nairobi East

SS Section J, page 171 / Lamu

400kV Extn Section J, page 170),

The OLTC shall be located at LV

line end with CFVV however as

per IEC 60076-8, Fig-7, Page no

25, OLTC at LV line end can be

achieved with two possible

configurations.

Configuration (a) : Voltage

variation at HV side.

Configuration (b): Voltage

variation at LV side.

Please confirm the required

configuration. ”

At the first instance the bidders shall comply to the

technical specifications, and followed by IEC or other

relevant standards where there are ambiguties.

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25 General When Koma Rock substation is

going to be constructed by

others, we presume access road

to koma rock will also be

constructed by others and the

same access road can be used

for proposed Nairobi East

substation also. Please clarify

whether access road to be

provided in present scope or not.

Access road is part of Lot C scope and this was clearly

explained during the site visits.

26 PB-KET-2014-

L-104

As per the layout it is mentioned

as maximum sag should be less

than 5% of the span length. We

infer that this criteria should be

met only for conductor sag .

Please confirm.

Also, Please clarify at what

temperature and wind conditions

this criteria should be checked.

Please comply and carefully read the specifications and

bidders are expected to use thier technical know how to

offer solutions.

27 Section VI -

Technical

specification,

clause 3.4,

page 47 of 385

As per specification it is given as

" The use of bare, stranded,soft

drawn copper is preferred by

KETRACO." Hence we are

following the same and adopting

exothermic weld for the main mat

earth conductors and

compression type bolted joints for

the above ground earth

conductor. Please confirm.

Accepted but subject to approval during design review.

28 Price schedule As per mandatory spares BOQ in

price schedule , Item F, S.No

1,2,3,4, 400kV and 220kV current

transformer and capacitive

voltage transformer has to be

provided. But, which type and

with how many cores to be

provided is not mentioned.

Please mention the

corresponding price schedule

item number under 400kV and

220kV primary plant for which

spare is to be provided.

Please refer to revised price schedules in Addendum 03

(Lot C). It shall be cross referenced with the bid drawings.

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29 Vol 2 of 2

Technical

Specifications

clause 4.3.1.3 -

Page 65 of 385

4.3.1 - Page 63

of 385

Price schedule

1 Item 1.3 ,1.4 ,

2.2 , 2.3

As per specification

The 400kV earthing switches

shall be mechanically individually

operated, therefore furnished with

one manual operator per phase


shall be mechanically group


one manual operator per three

phases.


Earth switches shall be fitted with

power and manually operated

mechanisms.

As per price schedule,

Disconnector with integral

motorised earth switches.

Please clarify whether integral

motorised earth switches or

integral manual earth switches to

be provided with disconnector.

Shall be manual earth switch. Revised Price Schedule is

provided in Addendum 03.

30 Schedule 4

Item no 26.14

The control room size given in

price schedule is 42 x 30 m.

Please clarify whether the control

room can be optimised as per the

requirement or it should only be

of the size given in price

schedule.

The proposed building size is 60m x 22m, for the purpose

of the tender the bidders shall offer for the required size.

31 General Please provide the orientation of

the following 400kV and 220kV

line bays .

400kV

Nairobi East to Lamu

Nairobi East to Isinya

220kV

Nairobi East to Embakasi

Nairobi East to IBT 3

220/66/11kV 200MVA

Please refer to bid drawings.

32 General Please provide the building

layout.

- Store building layout

The bidders shall submit a proposed layout as part of their

offer for the required size.

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33 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

400kV Line bay CT:

As per SLD, one stub protection

is required with 5 core CT.

As per specification, both 400kV

connections -1 with stub

protection 1 and 400kV

connections -2 protection with

stub protection 2 is required with

6 core CT.

Please confirm whether 5 core

CT(as per SLD)) or 6 core CT(as

per specification) to be

considered.

STUB protection is not duplicated and therefore one set of

protection relay and CT is suffcient as shown in the SLD.

The revised technical specification will uploaded as

adddendum.

34 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

400kV Bus CT:








5 core CT.

Please confirm whether the SLD

(4 core CT) or specification (5

core CT) to be considered.

See item 33.

35 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

400kV Tie CT:








3 core CT.




See item 33.

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36 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

400kV shunt reactor bushing CT:

Please confirm whether the core

1: 87-1/64REF required is of type

class 5P20 or PX.

Class PX.

37 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

220kV CT:

Since core 1 of CT shall be used

for stub protection, CT core 1

shall be of type "PX". Please

confirm.

Class PX.

38 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

Bushing CTs on HV side:








5 core CT.



core CT) shall be considered.

See item 33.

39 KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

Bushing CTs on LV side:








5 core CT.


(4-core CT) or specification (5-


See item 33.

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40

KET-2014-D-

001_Nairobi

East 400kV

SLD &

Protection Rev

3

Price schedule

1 Item Nos : 3.4

Lot C_Tech

Spec_Section

V, Clause

8.2.4.1,

400/220kV

Auto-

transformers

(400kV side), d.

400 kV HV

connections

protection.

Bushing CTs on HV side:

As per SLD, CT is with 4 core.

core 1: 87-1/64 REF, Cl 5P20

core 2: BCU/POW

core 3:50/51

core 4:STUB

In order to meet the protection

requirement as per price

schedule and Specification,the

following is considered

core 1: 87-1/64 REF, Cl PX

core 2: BCU/POW

core 3:50/51

core 4:HV connections -1

core 5:HV connections -2

Please confirm whether 4-core

CT or 5-core CT is required.

See item 33.

41 Lot C_Tech

Spec_Section

V, Clause

8.2.2,

substation

optical cables

and termination

Please confirm whether the

OPGW termination block (TB) is

in Substation contractor scope or

in overhead line contractor

scope.

This shall be part of Overhead lines contractor scope.

42 General Please clarify whether pre-

insertion resistor is required for

the following line bays.

400kV

Nairobi East to Lamu

Nairobi East to Isinya

220kV

Nairobi East to Embakasi

No. Please read TAC 1 item 70.


C Technical

List No.01

Q.No 109 & 96

Response to Q.No 109 says

control room has space provision

to accommodate protection and

control panels.

Response to Q.No. 96 says new

control building 40 x 32 m has to

be constructed.

Please clarify which one to be

followed.

New building shall be provided as Q.No. 96.

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C Technical

List No.01

Q.No 1

As per price schedule, 1 x 90

MVA three phase auto

transformer

As per datasheet , Three single

phase auto transformers.

Please clarify whether the

autotransformer is single phase

(90MVA) or three phase (90

MVA).

3 phase.


C Technical

List No.01

Q.No 60

Please clarify whether the neutral

earthing resistor rating shall be

1050 A for 30 sec or 500 A for 10

sec.

See item 10.

46 Cl.no 19.17.9,

Vol 2 of 2 Page

354 of 385

Galvanized steel elements

exposed to seawater spray, those

located in the seawater structures

and those in drainage sumps etc

shall be suitable for a Class C5

exposure as defined in BS EN

ISO 14713.

we presume same class is

appliccble for Lamu ie average

galvanization thickness is 115 µm

(micron).

Please confirm

Yes.


C Technical

List No.01

Q.No 55

As per clarification reply ,

Minimum capacity of tertiary

winding shall be 1/3 of main

winding capacity.

Hence, Main winding 3 ph

Capacity(Full cooling) - 90 MVA

Tertiary winding 3 ph capacity -

90/3 - 30 MVA

External loading - 0.5 MVA

Total capacity of tertiary winding

3 ph - 30.5 MVA

But as per transformer datasheet

, 70 MVA is given.

Please clarify and update the

datasheet.

See item 12.

48 General As the external loading of the

tertiary winding is 500 kVA , we

presume transformer tertiary

bushing shall be rated for the

same. Please confirm.

See item 13.

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49 Price schedule

: LOT C - Lamu

400/220kV Ext,

Appendix.2

Item No: 3.1,

400kV line

feeder

protection

Item No: 5

SCS,Telecomm

unication &

Associated

Equipment.

400kV Line bays:

(i)Lamu - Nairobi East-1

(i)Lamu - Nairobi East-2

From the price schedule, we

understand that no line

protection panel and

telecommunication works are

applicable for Lamu-1 & Lamu-2

400kV line bays.

Please confirm.

Correct.

50 Price schedule

: LOT C - Lamu

400/220kV Ext,

Appendix.2

Item No: 5

SCS,Telecomm

unication &

Associated

Equipment.

220kV Line bay:

Lamu - Hindi


presume that there is no

telecommunication work is for

Hindi 220kV line bay.

Please confirm.

Telecommunication work as specified in price schedule

item 5.5.


C Technical

List No.01

Q.No 1

As it is an extension substation ,

we don’t anticipate any of the

following items in present scope.

Item 26.8 Substation perimeter

fence including security

Item 26.9 Plot perimeter fence

Item 26.13 Substation

gatehouseItem

26.12 Substation

compound/perimeter lighting

26.14 Substation control / relay

buildingItem

26.17 Sewage SystemItem

26.18 CarparkItem

31.6 Single Unit staff houseItem

31.7 Double Unit staff houseItem

31.9 Access road outside the sub

stationand also, for the items that

are not listed here , we assume

that we only conduct the works

related to the 400/220kV

transformer and the 400kV shunt

reactors bays.

Please re-check and confirm,

Please read TAC 1.

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52 (Lamu 400kV

Extn Section J,

page 170)

“As per Technical data sheets of

Power transformer (Lamu 400kV

Extn Section J, page 170), The

OLTC shall be located at LV line

end with CFVV however as per

IEC 60076-8, Fig-7, Page no 25,

OLTC at LV line end can be

achieved with two possible

configurations.

Configuration (a) : Voltage

variation at HV side.

Configuration (b): Voltage

variation at LV side.

Please confirm the required

configuration. ”

See item no. 24.

53 Section VI -

Technical

specification,

clause 3.4,

page 47 of 385


" The use of bare, stranded,soft









See item 27.

54 Vol 2 of 2

Technical

Specifications

clause 4.3.1.3 -

Page 65 of 385

4.3.1 - Page 63

of 385

Price schedule

1 Item 1.3 ,1.4 ,

2.3










phases.




mechanisms.



motorised earth switches.


motorised earth switches or



See item 29.

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55 Lot C_Tech

Spec_Section

V, Clause

8.2.2,

substation

optical cables

and termination





scope.


56 Cl.no 19.17.9,

Vol 2 of 2 Page

354 of 385

Galvanized steel elements

exposed to seawater spray, those

located in the seawater structures

and those in drainage sumps etc

shall be suitable for a Class C5

exposure as defined in BS EN

ISO 14713.

we presume same class is

appliccble for hindi SS ie average

galvanization thickness is 115 µm

(micron).

Please confirm.

Yes.

57 Price schedule

: LOT C - Hindi

220kV Ext,

Appendix.D.3

Item No: 5

SCS,Telecomm

unication &

Associated

Equipment.

220kV Line bay:

(i)Hindi - Lamu


presume that there is no

telecommunication work is

applicable for lamu 220kV line

bay.

Please confirm.

See item 50.

58 General As per site visit , the distance

between Hindi and Lamu

substation is 25km but as per

specification, it is 20km. Please

clarify which one to be followed.

Distance by road may differ the distance taken by the line

route.

59 Section VI -

Technical

specification,

clause 3.4,

page 47 of 385


" The use of bare, stranded, soft









See item no. 27.

60 General Please provide the orientation of

the proposed 220kV extension

line bay

from Lamu to Hindi

Please refer to bid drawings.

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61 Vol 2 of 2

Technical

Specifications

clause 4.3.1.3 -

Page 65 of 385

4.3.1 - Page 63

of 385

Price schedule

1 Item 2.2 , 2.3










phases.




mechanisms.



motorized earth switches.


motorized earth switches or



See item no 29.

62 General Please provide the existing

busbar and line bay

conductor/tube details so as to

comply with the same for

extension bay also.

Existing drawings for Hindi is provided in the Addendum

No. 3 (Lot C).

63 General Please provide the existing

outdoor luminaires details so as

to comply with the same for

extension bay also.

Please refer to the technical specifications and it is

expected the bidders to take advantange of the site visits

to understand the existing site conditions.

64 General Please provide the overall layout.

- Existing drainage layout and

section

Please refer to Addendum 03 (Lot C)

The contractors shall survey and design the drainage

layout and section during the implementation stage

65 General Kindly provide the Finished

ground level (FGL) of the existing

substation for maintain the same

level for the extension area

Bidders shall assume the most practical FGL as per the

site visit

66 Lot C_Tech

Spec_Section

V, Clause

8.2.2,

substation

optical cables

and termination





scope.


67 Where possible these details are provided in the

addendums.

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68 First part of the question is answered in TAC 1.

Appendix C.1, C.2 and C.3 should read as follows:

1. 300MVA, 400/220/11kV for Nairobi East

2. 90MVA, 400/220/11kV for Lamu

3. No requirements at Hindi

69 See read TAC 1.

Technical Specifications , section 7.1 paragraph 1,

Bidders are expected to carry out insulation studies which

will produce the required surge arrester characteristics.

For the tendering purpose the bidders shall use MCOV of

289kV and with a TOV of 1.6pu. The actual TOV value is

subject to the outcome of the insulation studies which will

be determined during the design review.

70 TAC Item No. 86 It was stated as follows:

No. Stub Protection is for the Tie

Bus. Stub Protection

shall be used for OHL bay while

HVC shall be used in

Transformer bays.

STUB protection is the same as Connections Protection.

71 It is provided in Section G of the Technical Data sheet.

72 Please refer to shunt reactor specifications and technical

data schedules. The bidders are also advised to refer to

the relevant IEC documents where applicable.

73 Please read TAC 1, TAC 2 and Addendum 03 (Lot C)

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Sr.




74 In the bidding document, Clause

11.3.2.3, volume 2 of 2, the

110kV battery chargers has been

defined to be thyristor controlled

devices, but after contact with

some manufacturers with good

reputation, we found that the

thyristor controlled devices has

been out of production due to

technology improvement. now

most of the battery chargers are

high-frequency switch type. so

we advise to use the the high-

frequency switch type instead of

the thysistor controlled type.

Please comply as required in the specifications.

75 Please clarify the contradiction:

According to item No.85 of TAC-

2, "Hindi is installed with SCS.”

But in the attached drawings of

TAC-2, there is a "RTU560A" in

the drawings "SCADA

ARCHITECTURE" and "SCADA

PANEL FRONT

ARRANGEMENT DIAGRAM" of

"KENYA POWER

DISTRIBUTION SYSTEM

MODERNIZATION AND Hindi

220/33kV Substation". which one

shall us follow?

SCS is a term commonly used in KETRACO to describe

the Substation Automation and Control System.

Regardless the system employs computer or non-

computer topology, it is called as SCS. However to avoid

any further ambiguties, the employer wish to use the

following terminology for SCS:

a. RTU Topology (without BCU)

b. HMI Topology (with BCU)

The existing system in Hindi uses ABB RTU 560A which

has an integrated HMI (Human Machine Interface) for

supervision and control. The system is RTU based

topology, which is without a station level or bay computer

unit (BCU).

For the purpose of the tender the bidders shall follow the

existing drawings which indicates existing system at Hindi

is RTU Topology (without BCU).

76 For the optical fiber

communication system, we

noticed that the 400kV

transmission line between Nairobi

East substation and Lamu

substation is approximate 520km,

according to our experience, a

relay station must be arranged to

enhance the fiber communication

system. shall we take this relay

station into our bid price or there

is other contractor who will

conduct this work?

Please include in this bid

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Sr.




77 Hindi For Hindi 220kV substation,

Please provide the layout

drawings with proposed

extension scope, we cannot know

the location of the extension bay

so we cannot know the related

work of this extension.

Please refer to Addendum 03 (Lot C)

78 Volume 2 of 2 &

Pre-bid Replies

from KETRACO

Clarification

Lot C

Technical List

No.02, Item

No:4

Lot

C_Appendix

C.1_Schedule

of Technical

Particulars_N

East_Rev

1_25-05-15

As per the clarification, "For the

purpose of tendering the bidders

shall consider 10% impedance

and a tapping range of 400kV

+5/-15%/220kV."

However vendors confirmed that

this transformer with 10%

impedance is not possible and

even as per IEC 60076-5, page

no: 13, Table -1, Above 100 MVA

rating, minimum short circuit

impedance of the transformer

shall be >12.5%.

As per the Appendix-C Technical

Schedules ,

Hence, please suggest final %

impedance voltage (75degC),

rated frequency and full rating

required for the subject tender ,

- At principal tapping

- At maximum voltage ratio

- At minimum voltage ratio

IEC clearly states it is possible if the purchaser requires a

lower value. Therefore for the purpose of the tender

bidders shall use the specified values and ratings.

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