APERC - Grid Code

The Code of Technical Interface is a document that defines the boundary between APTRANSCO and Users and establishes procedures for operation and development of facilities connected to the Transmission system. It lays down both the information requirements and procedures governing the relationship between APTRANSCO and Users.

The C.T.I. shall be complied with by APTRANSCO, in its capacity as holder of the Transmission and Bulk Supply Licence, and by Generators, Distribution Companies, Suppliers and Bulk Power Consumers in the course of their activities in generation, supply, and utilization of electricity and in the capacity as holders of Retail Supply Licence.

The CTI is designed to facilitate the development, operation and maintenance of an efficient, co-ordinated and economical AP State transmission system by specifying to all parties connected to that system, including APTRANSCO, their technical and procedural obligations. It seeks to be non-discriminatory and to ensure that interfaces are not areas of weakness in the supply chain.

The Transmission and Bulk Supply License requires APTRANSCO to prepare and continually maintain in force, a Grid Code (or Code of Technical Interface)

Section 18 (Part III) of the License issued by APERC to APTRANSCO is reproduced below:

“Section-18 Grid Code

18.1 Except as provided in paragraph 18.4, the Licensee shall ensure that, within six months from the issue of the Licence, there is in force at all times a Grid Code, which meets the requirements of this paragraph 18. Subject to Paragraph 18.11, the Licensee shall implement and comply with the Grid Code.

18.2 The Grid Code shall include:

(a) All material technical aspects relating to, connections to, and the operation and use of the Transmission System including the operation of electric lines and electrical plant and apparatus connected to the Transmission System in so far as relevant to the operation and use of the Transmission System including, but not limited to connections specifying the technical, design and operational criteria to be complied with Transmission System or by any Generating Company who is connected with or seeks connection with the transmission System or the Distribution System of any Supplier.

(b) An Operating Code, specifying the conditions under which the Licensee shall operate the Transmission System and under which Generating Companies shall operate their plant and the Suppliers shall operate their Distribution System, in so far as necessary to protect the security and quality of supply and safe operation of the Transmission System under both normal and abnormal operating conditions.

(c) A Planning Code, specifying the technical and design criteria and procedures to be applied by the Licensee in the planning and development of the Transmission System;

(d) A Scheduling and Despatch Code specifying the system for the scheduling and despatch of Generating Sets.

(e) Procedures relating to the co-ordination of outages for scheduled maintenance of Generating Sets and transmission and distribution circuits;

(f) A Metering Code, setting out requirements and procedures for metering, and

(g) A Protection Code, setting out the requirements and co-ordination of protection systems.

18.3 The Grid Code shall:

(a) be designed so as to permit the development, maintenance and operation of an efficient, coordinated and economical system for Transmission and Bulk supply in the state of Andhra Pradesh; and

(b) allow the Licensee to comply with its obligations in relation to the inter–state transmission of power.

18.4 Where no Grid Code in the form provided for in this paragraph 18 is in force at the effective date of this license it shall not be considered a breach of this paragraph 18 provided that:

(a) the Licensee shall file with the Commission a compilation of the Interim Grid Code within 60 days of the grant of this License;

(b) the Licensee shall implement and comply with the Interim Grid Code from the date of its submission to the Commission, subject to such modifications as the Commission may direct; and

(c) Within six months of the commencement of this License, the Licensee shall submit the comprehensive Grid Code described in Paragraph 18.2 and 18.3 for the approval of the Commission, which must be formulated by the Licensee after consultation with Suppliers, Generating Companies, Distribution Licensees, Central Transmission Utility, Regional Electricity Board and such other Persons as the Commission may direct.

18.5 The Interim Grid Code shall continue to remain in effect until such time as the Commission has approved the final Grid Code.

18.6 The Licensee shall, in consultatant with Distribution Licensees, Generating Companies, the Central Transmission Utility, the Regional Electricity Board and such other persons as the Commission may specify, review the Grid Code and its implementation from time to time. The Licensee shall also undertake such review as and when directed to do by the Commission. All the representations received during the interim period shall be considered by the Licensee.

Following any such review, the Licensee shall send to the Commission:

(a) a report on the outcome of such review;. and

(b) any proposed revisions to the Grid Code from time to time as the Licensee reasonably thinks fit for the achievement of the objectives referred to in paragraph 18.2 and

18.7 All revisions to the Grid Code shall require the prior written approval of the Commission.

18.8 The Commission may issue directions requiring the Licensee to revise, supplement or replace the Grid Code in such manner as may be specified in the directions, and the Licensee shall comply with any such directions.

18.9 The Licensee shall make available a copy of the Grid Code in force to any person requesting it at a price not exceeding the reasonable cost of duplicating it.

18.10 In preparing , implementing and complying with the Grid Code (including in respect of the scheduling of maintenance of the Transmission System), the Licensee shall not unduly discriminate against or unduly prefer:

(a) any one or any group of Persons or

(b) itself in the conduct of any business other than the Transmission Business.

18.11 The Commission may issue directions relieving the Licensee or (following consultation with the Licensee) third parties of their obligations to implement or comply with the Grid Code to the extent as may be specified in the directions.”

The Code of Technical Interface is not concerned with the detailed design and operation of the Generator’s Power Stations and Supplier’s Distribution systems, provided that their overall compatibility with the needs of the Grid is assured. The responsibilities of the entities are defined and demarcated. Similarly, the CTI is not meant to be the internal operating instructions of APTRANSCO's transmission system.

1.1.2 Interpretation

The meaning of certain terms (which are usually printed in bold letters and/or capitalized) used in the Code of Technical Interface (CTI) shall be in accordance with the definitions listed in Section 1.2, “Definitions” of the C.T.I..

1.1.3 Implementation and Operation of the C.T.I.

APTRANSCO has the duty to implement the Code of Technical Interface (CTI). All Users are required to comply with the CTI, which will be enforced by APTRANSCO. Users must provide APTRANSCO reasonable rights of access, service and facilities necessary to discharge its responsibilities in the User’s premises. Users shall comply with instructions issued by APTRANSCO which are reasonably required to implement and enforce the Code.

If any User fails to comply with any provisions of the C.T.I., the User shall inform APTRANSCO without delay of the reason for its non-compliance. Repeated failures to comply with the C.T.I. may lead to the disconnection of the User’s plant and/or facilities. The responsibility for the consequences of disconnection including payment of damages and compensation to consumers rests with the User who consistently violates the CTI.

The Operation of the C.T.I. will be reviewed regularly by the C.T.I. Review Panel in accordance with the provisions of the relevant Section of the C.T.I..

The C.T.I. contains procedures to permit equitable management of day to day technical situation in the Electricity supply system, taking into account a wide range of operational conditions likely to be encountered under both normal and abnormal circumstances, relevant both in the present conditions and future expanded system and in the present generation shortage period, as well as surplus generation period which may come in the future.

However, the C.T.I. cannot predict and address all possible operational conditions. APTRANSCO is therefore empowered in such unforeseen circumstances to act decisively to discharge its obligations under its License. Users shall provide such reasonable cooperation and assistance as APTRANSCO may request in such circumstances. It is to be recognized that the SLDC is required to make quick decisions for remedying Grid crises and the instant judgments and decisions may contain oversight errors. Post-event corrections shall be made by SLDC itself, taking into consideration the feedback from various stakeholders and consumers. The Users and consumers have the right to approach the Regulator for redressing their grievances and unfairness. All parties must first comply with the spot instructions of SLDC and if injustice is experienced, the matter shall be represented to SLDC. If SLDC does not carry out the necessary changes in the subsequent operation, the aggrieved party may complain to the APERC.

1.1.4 Code Responsibilities

In discharging its duties under the Code of Technical Interface, APTRANSCO has to rely on information which Users supply regarding their requirements and intentions. APTRANSCO shall not be held responsible for any consequences that arise from its reasonable and prudent actions on the basis of such information.

1.1.5 Confidentiality

Under the terms of the Code of Technical Interface APTRANSCO will receive information from Users relating to their intentions in respect of their generation or supply businesses. APTRANSCO shall not, other than as required by the Code of Technical Interface, disclose such information to any other person without the prior written consent of the provider of the information.

1.1.6 Dispute Settlement Procedures

In the event of any dispute between any Users and APTRANSCO, or between Users, regarding interpretation of any Clause of the Code of Technical Interface, the matter will be resolved according to procedures set up in this Code (Section 1.5). The Commission will be the final arbitrator whose decision shall be final and binding. In the event of any conflict between any provision of the Code of Technical Interface and any contract or Agreement between APTRANSCO and a User, the provision of the Code of Technical Interface shall prevail.

1.1.7 Communications between Licensee and Users

All communications between APTRANSCO and Users shall be in accordance with the provision of the relevant section of the Code of Technical Interface. Unless otherwise specifically required by the Code of Technical Interface, all communications shall be in writing, except where operation time scales require oral communication, in which case these communications shall be confirmed in writing as soon as practicable.

1.1.8 Partial Invalidity

If any provision or part of a provision of the Code of Technical Interface should become or be declared unlawful for any reason, the validity of all remaining provisions or parts of provisions of the Code of Technical Interface shall not be affected.

1.1.9 Directives

Under the provisions of the Act, the State Government may issue policy directives in certain matters. The Licensee shall promptly inform the Commission and all Users of the requirement of such directives. The Users, subject to the relevant section of the Act, shall comply with the directive.

1.2 Definition of Terms

In the Code of Technical Interface the following words abbreviations and expressions shall bear the following meanings:

TERM	DEFINITION
Act	The A.P. State Electricity Reforms Act 1998
Active Power or MW	Product of voltage and current and cosine of the phase angle between them measured in units of Watt (W) Kilowatt (kW) = 10³ W Mega Watt (MW) = 10⁶ W Giga Watt (GW) = 10⁹ W Tera Watt (TW) = 10¹² W
Active Energy	The electrical energy produced, flowing in or supplied by an electrical circuit during a time interval, being the integral with respect to time of Active Power, measured in units of watt-hours or standard multiples thereof, that is :- 1000 Wh = 1kWh = 1 unit 1000 KWh = 1MWh 1000 MWh = 1GWh = 1MU (Million units) 1000 GWh = 1 TWh = 10¹² Wh
A.C.	Alternating Current
Agreed Procedure	Procedure for dealing with specific situations in metering as specified in Section 5.2.3 of the Metering Code.
Alternator	The electrical machine which is driven by a prime mover and generates AC electric power. The term Generator is reserved for another meaning to avoid confusion (see def. of Generator)
Annual Hydro Plan	The plan prepared by APTRANSCO on the instructions of High Power Electricity Irrigation Coordination Committee by mid September each year relating to Water Resource Management during the period of twelve months commencing on 1st October in that year.
Apparent Power	S = P + JQ. Magnitude is calculated by the formula S = Ö(P²+ Q²) expressed in units of Volt-amps (VA) or multiples like kVA, MVA
A.P. Code of Technical Interface	The set of principles and guidelines prepared by APTRANSCO in accordance with the terms of the Transmission License, as amended from time to time by the direction of the Commission, relating to the Planning, Design and Operation of the APTRANSCO System and all Users connected to it.
APERC	Andhra Pradesh Electricity Regulatory Commission. (referred to as the ‘Commission’)
Apparatus	All equipment in which electrical conductors are used, supported or of which they may form part.
Appendix	An Appendix to a Section of the Code of Technical Interface
APGENCO or APGC	Andhra Pradesh Generation Corporation Ltd., registered under the Companies Act and successor of APSEB in generation of power
APTRANSCO or APTC	Transmission Corporation of A.P Limited, Registered in 1999 under the Act of 1998 which is the successor to APSEB in Transmission of Electricity and other general functions like coordinating all Power Sector entities in AP State.
APTRANSCO Control Centre	A location used for the purpose of control & operation of the APTRANSCO system which, on the transfer date is at Vidyut Soudha in Hyderabad, Andhra Pradesh
APTRANSCO Data Collector	A data collecting device owned by APTRANSCO which transmits data to the Data Collection System of APTRANSCO for the purpose of compiling information
APTRANSCO Demand	The Demand on the APTRANSCO system less the output of Independent Generating Plant limited to provision by the Connection Agreement
APTRANSCO Site	A Site owned by APTRANSCO, or owned by a User but occupied by APTRANSCO, in which there is a Connection point.
APTRANSCO System	The transmission system at voltage levels of 400 kV, 220 kV, 132 kV and 66 kV. (The Distribution system shall be treated as a separate entity of the Supplier.)
APTRANSCO System Data	Data concerning the APTRANSCO System to be supplied by APTRANSCO to Users. APTRANSCO system data consists of salient features to the existing system and future system as per the perspective plan. Such data shall contain details of EHV lines (i.e.132KV and above) and shall include the following: (a) Single line diagram of the APTRANSCO system indicating the existing lines and proposed lines (shown dotted). (b) Map of A.P showing the existing lines of the APTRANSCO system and proposed lines (dotted) preferably to scale 1Cm = 10 kM
Area of Supply	As defined in the license concerned.
Area Load Despatch Centre	One of the four stations in AP State being established under Southern Region System Coordination and Control Project, having as main functions: - Data acquisition and transfer to SLDC and supervisory control of 132 kV and 33 kV equipment.
Automatic Load Shedding	A Load shedding scheme implemented by APTRANSCO to prevent frequency collapse or other problems and to restore the balance between generation output and demand on the APTRANSCO system
Automatic Voltage Regulator (AVR)	A continuously acting automatic excitation system to control the voltage of a Generating Unit measured at the Generator Terminals
Back Supply	Supply of electricity to the APTRANSCO and for its own use
BIS	Bureau of Indian Standards.
Black start	The procedure necessary for a recovery from a Total Shutdown or Partial Shutdown.
BPTA	Bulk Power Transmission Agreement
Break-down	An occurrence relating to equipment of supply system which prevents its normal functioning
Cancelled start	A response by a Generator to an instruction from APTRANSCO canceling a previous instruction to synchronize to the APTRANSCO system
Capability	The Capability of a Generating unit, expressed in MW, to generate electricity determined at the Interconnection point (after deducting consumption of auxiliaries)
Captive Power Plant (CPP)	A Power Station which is primarily operated to meet a Captive Demand
CCGT Module	A group of Generating Units comprising one or more Gas Turbine Units and one or more Steam Units wherein the waste heat from the gas turbines is passed to the water/steam system of the steam units thereby increasing the overall efficiency of CCGT Module.
CEA	The Central Electricity Authority of India.
CCGT	Combined Cycle Gas Turbine
CCGT Unit	A Generating Unit within a CCGT Module
Central Despatch	The process of scheduling and issuing Despatch Instructions in relation to CDGUs direct to a Generating plant by APTRANSCO pursuant to the Code of Technical Interface
CERC	Central Electricity Regulatory Commission established under Electricity Regulatory Commission Act 1998 and Electricity Laws (Amendment) Act 1998 (Central Acts)
Central Sector Projects	Power Projects and Transmission Projects built and operated by Central Organisations such as National Thermal Power Corporation (NTPC), National Hydro Power Corporation (NHPC), Power Grid Corporation of India Limited (PGCIL)

Centrally Despatched Generating Unit or CDGU	A Generating Unit within a Generating Plant
Changed Status Data of a CDGU	Newly arisen factors pertaining to a CDGU and its parameters which may have a material effect on the probable output of a CDGU and which must promptly be intimated to the SLDC by the Generator concerned (Refer also “GSDP” Notice)
Civil Emergency	Any National disaster or other emergency which is declared by the State/National Government as one that is likely to disrupt Electricity supplies
Code of Technical Interface Review Panel	A standing body established by APTRANSCO to carry out the following functions. (a) Keep the Code of Technical Interface and its working under periodic review (b) Review any suggestions for amendments to the CTI at meetings of the panel held in accordance with the Panel’s constitution, and (c) Give guidance in relation to the Code of Technical Interface, its implementation, performance and interpretation on the reasonable request of any User.
Commission	The A.P Electricity Regulatory Commission established pursuant to Sec.3 of the A.P. Electricity Reforms Act 1998, same as APERC.
Confirmation Statement	A daily statement prepared by a Generator and submitted to APTRANSCO in accordance with the relevant PPA.
Connected Load	Aggregate of rated capacity of all apparatus including portable apparatus in the Consumer’s premises which are supplied or declared by the Consumer to be taking supply from the system. This shall be expressed in kW, kVA
Connection Agreement	An Agreement between APTRANSCO and a User setting out the terms relating to a connection to and/or use of the APTRANSCO system
Connection Conditions