isg130/01 metering dispensation d/371 - elexon · pdf fileisg130/01 metering dispensation...
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ISG130/01 v1.0
Page 1 of 2 © ELEXON 2011
ISG130/01
Metering Dispensation D/371
Meeting Name Imbalance Settlement Group (ISG)
Meeting Date Ex-committee – response requested by 5pm 15 November 2011
Purpose of paper For Decision
Summary
CE Electric have applied for a Metering Dispensation for a 12MW power plant where the
metering CTs and VTs are to be located at a distance from the Boundary Point. This paper
seeks ISG’s approval for the Metering Dispensation on the grounds of negligible materiality.
1. BSC Requirements
1.1 Section L 3.2 of the Balancing and Settlement Code (BSC) requires Registrant’s of Meter Equipment to
ensure that the Metering Equipment it uses for Settlement purposes is, and remains compliant with the
requirements of the relevant Codes of Practice (CoP). Section L 3.4 of the BSC has provision for Registrants
to submit an application for a Metering Dispensation where it is not possible, if for practical or financial
reasons, to comply with the requirements of a relevant CoP.
2. Background
2.1 Girlington power plant is a new 12MW station that is to be owned and operated by Green Frog Power
Limited as Short Term Operating Reserve.
2.2 During the process of application for connection to CE-Electric’s network it was established that costs in the
order of £1.5m would be required to accommodate Settlement current and voltage measurement
transformers (CTs and VTs). The bulk of these costs are associated with the provision of a new a 33kV
substation to accommodate additional HV switchgear containing CTs and VTs.
2.3 On 31 October 2011 we received an application for a Metering Dispensation in accordance with BSCP32
‘Metering Dispensations’ (Attachment A) from the requirements of Code of Practice 2.
2.4 The applicant proposes to locate the metering CTs and VTs in the customers 33kV switch gear (at a cost of
approximately £2,000) which is located 70 metres from the Defined Metering Point. The applicant has
assessed the electrical losses between the Boundary Point and the Actual Metering Point and concludes that
they are negligible and can be disregarded as they amount to a very small percentage of the allowable
accuracy of CoP2.
2.5 The applicant also assesses the materiality and risk to Settlement of approx 60-70kWh per year. This is
based on the electrical loss at full export capacity for an estimated run time of approximately 125 hours per
year.
ISG130/01 v1.0
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ISG130/01
2.6 We issued the application to the Metering Dispensation Review Group (MDRG) for comment and received 4
responses. All four members support the application.
2.6.1 One MDRG member queried whether the estimation of active power loss quoted at 0.05% was, in fact,
correct. The applicant has confirmed that this figure in the application should read 0.005%.
2.7 This MDRG member also noted that the estimation of electrical losses did not cater for no load loss. We
asked the applicant to comment on this and have received an amended calculated estimate of losses which
includes no load losses of 6.39W (Attachment B).
3. ELEXON's View
3.1 We believe that locating the CTs and VTs in the customer’s switchgear is a reasonable and cost effective
solution. We therefore fully support this application for Metering Dispensation on the grounds of negligible
risk to Settlement.
4. Recommendations
4.1 We invite you to:
a) NOTE the application and MDRG views; and
b) APPROVE Metering Dispensation D/371.
Attachments:
Attachment A – Metering Dispensation D/371 Attachment B - D371 Cable loss calculations
For more information, please contact:
Keith Campion, Metering Analyst [email protected]
020 7380 4011
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
ISG130/01 - Attachment A
EN3392 - Calculation of cable losses for Metering Dispensation Load current for 12MW export at 0.95 power factor:
kVAI L [email protected]
10123
6
Cable details Cable type: 3 x single core cables to BS7870-4.10 in Triplex Voltage: 33kV Cross-sectional area: 150mm2
Conductor length: 70m ac resistance R (90o) 0.159 ohms/km reactance (50Hz): 0.129 ohms/km sheath resistance Rs: 0.379 ohms/km Distance between cable centres S: 0.043m approx Mean diameter of sheath dm: 0.039m approx I = phase conductor current Conductor losses Active Power Loss per phase
222 0111.0701000
159.0IIRIPloss
Reactive Power Loss per phase
222 0090.0701000
129.0IIXIQloss
Dielectric Losses Dielectric losses are negligible compared to the conductor losses for cables up to 50kV, as the power factor of the cable insulation is of very low order. Dielectric losses are dependent on voltage and so will be present when the cable is energised even if it is not carrying load current. They are given by the following equation:
kmW
UCfP Od
/2.91
004.03
1033102.0502
tan..2
23
6
2
ISG130/01 - Attachment B
Sheath Losses The sheath losses are made up from eddy current losses and sheath circuit losses. For single core cables connected in triplex formation and bonded and earthed at both ends the eddy current losses will be negligible, however the sheath circuit losses should be taken into account. The sheath circuit losses are due to the e.m.f. which is induced in the sheath by the a.c. conductor current by transformer action, which causes a current to flow in the sheath. The sheath current losses per phase are given by the following equation:
22
2
2
sm
mssheathloss
RX
XRIP (BICC Cable Handbook, equation 2.16)
Where Xm is the mutual reactance of the sheath and can be calculated from
kmohms
kmohmsd
SLogfX
e
m
em
/0497.0
10039.0
043.02log2.0502
/102
2.02
3
3
For 70m run of cable, the sheath losses will therefore be:
2
22
22
0004.0
1000
70
379.00497.0
0497.0379.0
IP
IP
sheathloss
sheathloss
Actual Loses at 12MVA at 0.95PF
pfWP
IIRIP
loss
loss
0111.0701000
159.0
2
222
pfVarQ
IIXIQ
loss
loss
0090.0701000
129.0
2
222
pfWP
IP
sheathloss
sheathloss
0004.0
2
2
W
Pd
39.6
1000
702.91
ISG130/01 - Attachment B