Before the
MAHARASHTRA ELECTRICITY REGULATORY COMMISSION
World Trade Centre, Centre No.1, 13th Floor, Cuffe Parade, Mumbai – 400 005
Tel. No. 22163964/ 65/ 69 Fax 22163976
Email: mercindia@mercindia.org.in
Website: www.mercindia.org.in
Case No. 91 of 2007
In the matter of
Petition of Suzlon Power Infrastructure Ltd. seeking clarification/ amendment in the
Terms and Conditions of Tariff Regulations 2005 with respect to design of 220 kV
and 132 kV transmission lines with reference to wind energy sector.
Dr. Pramod Deo, Chairman
Shri. A. Velayutham, Member
Shri. S. B. Kulkarni, Member
ORDER
Dated: April 15, 2008
M/s. Suzlon Power Infrastructure Ltd. (SPIL) filed a Petition on January 16, 2008
seeking clarification / amendment in the MERC (Terms and Conditions of Tariff),
Regulations, 2005, related to design of 220 kV and 132 kV transmission lines pertaining
to the wind energy sector.
2.
The prayers made by the Petitioner are as follows:
(1)
Accept the Petition in the matter of clarification / amendment in the
Terms and Conditions of Tariff Regulation 2005 with respect to design of 220
KV and 132 KV transmission lines with reference to wind energy sector;
(2)
Modify / Amend its terms and Conditions Regulations 2005 with respect
to design of 220 KV and 132 KV transmission lines with reference to wind
energy sector;
(3)
Allow loading of the Transmission lines using ACSR Panther conductor
up to 440Amp and ACSR Zebra Conductor up to 700 Amp as per column 5 of
Table II A above;
(4)
Not to insist N-1 criteria for exclusive transmission of electricity from
Wind farms.
Since this matter
Commission directed the
accompaniments (both in
Maharashtra State Power
required the views of the immediate stakeholders, the
Petitioner to serve copies of its Petition along with its
hard and soft versions) to all the Distribution Licensees;
Generation Company Ltd. (MSPGCL); State Transmission
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Utility (STU), and the four consumer representatives authorised on a standing basis under
the Electricity Act, 2003 (“EA 2003”). The Commission further directed the Distribution
Licensees, MSPGCL and STU to file their reply to the said Petition on affidavit, if any,
with a copy endorsed to the Petitioner and to the four consumer representatives. Hearing
in the matter was scheduled by the Commission on March 25, 2008.
3.
At the hearing held on March 25, 2008, Shri. Atul Shah and Shri S V Deo appeared
for the Petitioner (M/s SPIL). Shri. V.T. Phirke represented the STU. At the outset,
M/s SPIL submitted that the Surge Impedance Loading (SIL) values specified in the
MERC (Terms and Conditions of Tariff), Regulations, 2005 at Appendix II are not in line
with the “Manual on Transmission planning criteria” issued by the CEA in June 1994 as
these values are not applicable to short lines.
4.
During the hearing, it was observed by the Commission that the SIL values specified
at Appendix II of the said MERC (Terms and Conditions of Tariff), Regulations, 2005
were for calculation of transmission system availability, which was in line with the
“Central Electricity Regulatory Commission (Terms and Conditions of Tariff),
Regulations, 2004”. In accordance with Section 61 of the EA 2003, the Commission is
required to be guided by the principles and methodologies specified by the CERC for
determination of the tariff applicable to generating companies and transmission licensees.
Hence, the SIL values are used for applying the incentives based on transmission system
availability. Therefore, M/s SPIL should not relate these values with SIL limits specified
in Manual on Transmission planning criteria issued by the CEA in June 1994.
Consequently, the issues raised by M/s SPIL with respect to design of 220 KV and 132
KV transmission lines with reference to wind energy sector would not require effecting
any amendment to the MERC (Terms and Conditions of Tariff) Regulations; 2005.
The other issues raised in the Petition are dealt with in the following paragraphs :
5.
Loading Limit: Regarding the issue of permissible loading limit of the
transmission lines installed for evacuation of Power from the generating stations,
M/s SPIL read out paragraph 6 of its Petition, which is in respect of CEA Manual
on Transmission Planning Criteria – Section 4: “Permissible line loading Limits”.
The same is reproduced below:
“Permissible line loading Limit depends on many factors such as voltage
regulation, stability and current carrying capacity (thermal capacity) etc. While
Surge Impedance Loading (SIL) gives a general idea of the loading capability of
the line, it is usual to load the short line above SIL and long lines lower than SIL (
Because of the stability limitations). SIL at different voltage level is given at
Annex-II. Annex-II also shows line loading (in terms of surge impedance loading
of uncompensated line) as a function of line length assuming voltage regulation of
5% and phase angular difference of 30 0 between the two ends of the line. In case
of shunt compensated lines, the SIL will get reduced by a factor K, where
K = (1-degree of compensation )-1/2
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For lines whose permissible line loading as determined from the curve is higher
than the thermal loading limit, permissible loading limit shall be restricted to
thermal loading limit.”
6.
Redundancy Criteria: M/s SPIL requested for a clarification regarding
applicability of redundancy criteria in the network i.e. (N-1) redundancy condition,
to the transmission lines used for evacuation of Wind Energy. It was submitted that
as per the CEA guidelines, under steady State operation, the EHV Grid System
should be capable of withstanding without necessitating load shedding or rescheduling of generation the following contingencies:
v Outage of a 132 kV Double Circuit line; or
v Outage of a 220 kV Double Circuit line.
7.
As per M/s SPIL, if one transmission line circuit goes out, the other transmission
line circuit would be adequate for power evacuation as the Double Circuit transmission
lines are designed with built-in redundancy accordingly. As per M/s SPIL, healthiness
and availability of one transmission line, in the event of the loss of a single transmission
line from a double Circuit transmission network is enough to meet out the (N-1)
redundancy condition as against the requirement of one complete Double Circuit to be
kept redundant.
8. M/s. SPIL further submitted that 2.5 times of the SIL loading can be accommodated
on the transmission line in case of contingencies because wind energy generation which
is an infirm power, has its peak period during the monsoon months of June-July-August.
It is known that during these periods, the ambient temperature is low, and heat
dissipation from the current carrying conductors is better facilitated by the winds. As a
result, these parameters permit more ampacity (ampere capacity) within the limits of
Thermal loading of the lines. M/s. SPIL further requested the Commission to issue
directive to raise permitted line loading to 700 Ampere and 400 Ampere for ACSR
Zebra and Panther Conductors, respectively. M/s SPIL submitted that Ampere should
be the basic criteria for designing the transmission lines as the Ampere flow is
responsible for the temperature rise.
M/s. SPIL further explained that the wind power generation projects, generally, are at
the periphery of the Intra-state transmission system (grid) and these are radially
connected through transmission lines to the Intra-state transmission system. Hence, the
main network parameters of the Intra-state transmission systems are not much
influenced by the contingencies on the Wind power evacuation system.
9. The Commission enquired with Shri V.T. Phirke who represented the STU at the
hearing, Shri Prashant Joshi who was present on behalf of The Tata Power Company Ltd
and Shri B.S. Chaudhari who was present on behalf of The Reliance Energy Ltd.,
regarding their views pertaining to the issues raised by M/s SPIL. However, the
representatives of the STU and the other utilities submitted that copy of the Petition was
received by them only on 24th March, 2008 and hence, they were not in a position to
comment on the same due to paucity of time.
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10. The Commission is of the view that two main issues emerge from the submissions
made by M/s. SPIL, that is (i) to allow line loading more than SIL for short lines and (ii)
relaxation in the (N-1) redundancy criteria in respect of wind power evacuation projects.
The Commission is of the view that both these items are governed by Grid standards and
the standards for construction of transmission lines, which are dealt with by the CEA in
line with section 34 and section 73(b) of EA 2003. The Commission is of the view that
the STU is supposed to discharge all functions of planning and co-ordination related to
Intra-State Transmission system with the CEA / CTU / Transmission Licensees /
Generating Companies (including Renewable Energy Projects) etc., in accordance with
section 39(2)(b) of the EA 2003.
11. The Commission observes that the issue of Line loading above SIL has already
been addressed in the CEA’s manual on Transmission Planning criteria where it is stated
that “…. it is usual to load the short lines above SIL…… permissible loading limit shall
be restricted to thermal loading limit”
It should also be noted that, for such loading above SIL limits, the need for
providing reactive compensation, if called for, to avoid possible voltage drops should be
addressed after conducting the required studies. Higher SIL may be permitted only after
taking into account the capability limits of the conductors based on present observations
of relevant National / International bodies.
12. The Commission further observes that in case of (N-1) redundancy condition, the
STU may arrive at appropriate decision in consultation with the CEA. For Renewable
Energy Generation Project, general specifications which are directed for the
conventional transmission systems may not be applicable to these transmission lines and
specific conditions need to be considered after due evaluation, keeping in mind their
limited impact on the Intra-state transmission network.
13. In this context, the directives given by the Commission in its Order dated
November 13, 2007, in the matter of “In principle approval to Maharashtra State
Electricity Transmission Company Limited for development of infrastructure facilities to
enable evacuation of power” (Case No. 34 of 2007), are relevant to be quoted as below:
Item 29. “As outlined under earlier paragraphs, the Evacuation Arrangement
including transmission lines for evacuation of power from generating station forms
part of the Intra-State Transmission system. In this regard, the Commission further
clarifies that being part of InSTS, the expenditure incurred for development of such
transmission infrastructure shall form part of total transmission system cost of
InSTS independent of who develops such transmission infrastructure. The same
shall be recovered in accordance with the principles outlined under Transmission
Pricing Framework Order of the Commission. Thus, question of differential
treatment for evacuation arrangement for generating stations depending on
ownership of the generating station does not arise, so long as generating station
uses state transmission network for wheeling power to distribution licensees or
open access users within State.”
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14. As elaborated under Paragraph 24 and 25 of the Commission’s Order dated
November 13, 2007 (Case 34 of 2007) as well as under Regulation 8.6 and 8.7 of MERC
(Transmission Open Access) Regulations, 2005, the Commission reiterates that as per
Section 39(2)(b) of EA 2003, MSETCL in its capacity as STU is responsible for
development of State-wide Transmission System Plan and to ensure co-ordinated
development of intra-State transmission system. In fact, the Planning Code and Planning
Criteria outlined under relevant Regulations 8 and 9 of “MERC (State Grid Code)
Regulations, 2006 shall form the basis for STU to discharge its statutory function of
planning.
15. Further, as per Section 86(1)(e) of EA 2003, the Commission is obliged to promote
generation from renewable energy sources by providing suitable measures for
connectivity with the Grid for such renewable energy sources. Accordingly, the
Commission advises the STU that while applying norms for Renewable Energy Sources,
it should be borne in mind that the project for evacuation arrangement should be
financially feasible and capital expenditure burden should be optimum, which in turn,
will benefit the consumers and help in promoting Renewable Energy Projects.
However, the Commission cautions that in no case the technical and safety requirements
should be diluted and that there should be sufficient flexibility to consider the specific
conditions.
16. During the hearing, the STU had submitted that they had not evaluated the above
aspects associated with the development of evacuation arrangement for renewable
energy sources. The Commission therefore directs STU to evaluate the issues pertaining
to (a) Loading limits; and (b) Redundancy criteria, applicable to the short transmission
lines evacuating the Wind power, which are presented by M/s SPIL. The Commission
further directs STU to explore the appropriate solution and communicate to the
petitioner within six weeks time from issuance of this Order, under intimation to the
Commission.
With the above observations and directions, Case No. 91 of 2007, stands disposed of.
Sd/(S.B.Kulkarni)
Member
Sd/(A. Velayutham)
Member
Sd/(Dr. Pramod Deo)
Chairman
(P.B.Patil)
Secretary, MERC
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