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DISTRIBUTION SYSTEM PLANNING AND SECURITY STANDARDS, 
OPERATING STANDARDS, UNDER CONDITION - 20 
OF THE ORISSA DISTRIBUTION AND RETAIL SUPPLY 
LICENCE - 1999 (No.1/99, 2/99, 3/99 and 4/99)

1.TITLE

1.1 These standards may be called as:

  1. Distribution System Planning and Security Standards.

  2. Distribution System Operating Standards.Go Top

 

1.2 Definitions:
For these standards, terms (which are printed in bold letters) shall mean the following unless the context otherwise requires, the words or expresions occuring in these standards of performance, shall bear the same meaning as in OERC Act l995, OERC (Conduct and Business) Regulations 1996, Rules and Licenses. New Terms, words and expressions occuring in these standards which have no definite meaning be defined under the heading-Reference.

CBI & P Manual: Manual published by central Board of Irrigation and Power, a Technical body of the Government of India.

KVA-KM Loading: Capacity of a line to deliver a certain load in KVA for a certain distance in KM with certain Voltage Regulation and Power Factor.

P.G. Clamps: Parallel Groove Clamps used for conductor jumper connection.

R.E.C. Specification: Specification issued by Rural Electrification Corporation Ltd. (A Government of India Undertaking).Go Top

 

2. APPLICATION

2.1 Distribution System Planning and Security Standards
These standards shall apply to the Licensee's Distribution System under Condition 20.1(a) of the License. The Licensee shall plan and develop its Distribution System in accordance with these standards together with the Distribution Code. The consumers shall cooperate with the Licensee in furnishing data regarding loads they wish to connect to the Distribution System, as required by the Licensee.Go Top

 

2.2 Distribution System Operating Standards
These standards shall apply to the Licensees Distribution System under Condition 20.1(b) of the License. The Licensee shall operate the Distribution System in accordance with these standards together with the Distribution Code.Go Top

 

2.3 The standards applicable to Distribution System at EHT shall be the same as provided under power supply planning and security standard, operating standard, power supply operating standard approved by the Commission under Condition 20 of Transmission and Bulk Supply License.Go Top

 

3. REFERENCE

These standards also require reference to the following Acts, Rules, Codes etc.

  1. The Indian Electricity Act, 1910,

  2. The Electricity (Supply) Act, 1948,

  3. The Indian Electricity Rules, 1956,

  4. The Orissa Electricity Reform Act, 1995,

  5. The Distribution Code,

  6. REC Specifications and Construction standards,

  7. CBI&P manual on Layout of sub-stations.

  8. Power supply planning and security standard, operating standard, power supply operating standards approved by the Commission under Condition 20 of Transmission and Bulk Supply License.Go Top

 

4. DISTRIBUTION SYSTEM PLANNING & SECURITY STANDARDS

4.1 General:

4.1.1 The Licensee shall plan and develop its Distribution System, particularly to ensure that subject to the availability of adequate generating and transmitting capacity, the system is capable of providing consumers with a safe, reliable, economical and efficient supply of electricity.

4.1.2 The Licensee's Distribution System shall conform to the statutory requirements of Indian Electricity Act 1910, Electricity Supply Act 1948, and Indian Electricity Rules 1956.Go Top

 

4.2 Planning Procedure:

4.2.1 The Licensee shall prepare a long term load forecast for a period of 5 (five) years in its Area of Supply taking into account the probable load growth and consumption pattern of the consumers. The Licensee shall adopt appropriate load forecasting methods using reliable data and relevant indices. The methods may include one or more of the following methods.

  1. Econometric regression analysis.

  2. Appliance saturation methods.

  3. End-use energy methods.

  4. Any other reasonable and justifiable method.

4.2.2 Consumers seeking to contract demands of 5MW and above shall submit application to the Licensee along with load data in the manner to be prescribed by the Licensee in conformity with Distribution Code, as follows :

  1. For contracting Loads up to l0 MW - 3years in advance

  2. For contracting Loads in excess of 10 MW - 5years in advance

4.2.3 The consumers shall inform in writing to the Licensee promptly regarding changes, if any, in their load demand and its scheduling.

4.2.4 The Licensee shall work out the annual Energy Demand and Peak Demand for each of the succeeding five years relating to each point of interconnection on the basis of its load forecast.

4.2.5 By suitable sampling and installation of meters the Licensee shall workout the Diversity Factor/Coincidence Factor of each class of consumers fed from each point of interconnection in the area of supply. The Licensee shall maintain a record of such data and update the same at last once in 5(five) years. The licensee shall prepare the long term load forecast based on these data as refered to in para 4.2.1.

4.2.6 The Licensee shall arrange to publish a Data Book listing all System Data relating to its Distribution System as detailed in the Distribution Code. The Data Book shall be updated every year and copies of same shall be made available to any effected person upon request on payment of fair copying charges:Go Top

 

4.3 Planning Standards Criteria

4.3.1 Standardization of Sizes and Ratings
For each voltage class of application such as 230/400Volts, 11,000 Volts, and 33,000 Volts, conductors, insulators, lightning arresters, transformers, switchgear, etc. used in the Distribution System shall be standardized with the objective of reducing the inventory. Specifications for these materials shall at least conform to relevant Indian standards in general.

4.3.2 Standardisation of Sub-Station Layouts
The Licensee shall develop standard layouts to fulfil the minimum requirements detailed below.

4.3.2.1 33/11kV Sub-Station (20MVA and above)

  1. The layouts shall generally conform to CBI&P manual on Layout of Sub-Stations as applicable and provisions in Indian Electricity Rules, 1956 subject to the requirements mentioned in Sub paragraph (b), below

  2. The layout adopted shall include the following :-

  1. Independent Circuit Breaker control of 33kV Feeders and Transformers.

  2. Independent Circuit Breaker control of 11KV Feeders.

  3. Provision of Tariff and Operational metering in accordance with Distribution Code.

  4. Single bus sectionalised.

4.3.2.2 33/11kV Sub-Station (10 MVA above but less than 20MVA)

  1. The layout shall generally conform to relevant Construction Standards of Rural Electrification Corporation Ltd. and provisions in Indian Electricity Rules, 1956 subject to the requirements mentioned in Sub-paragraph (b) below.

  2. The layout adopted shall include the following :

  1. Independent Circuit Breaker control of 33kV Feeders and Transformers.

  2. Independent Circuit Breaker in each of 11KV Feeders.

  3. Single Bus Sectionalised.

4.3.2.3 33/11kV Sub-Station (Less than 10MVA)

  1. The layout shall generally conform to relevant Construction Standards of Rural Electrification Corporation Ltd / any other improved standards and provisions in Indian Electricity Rules, 1956 subject to the requirements mentioned in sub paragraph (b) below.

  2. The layout adopted shall include the following :

  1. Group circuit Breaker control of Transformers.

  2. Independent control of 11KV Feeders.

  3. Single Bus.

4.3.2.4 11/0.4kV 3-phase Distribution Transformer Centres

  1. Transformers up to 200 KVA capacity other than those meant for indoor application shall normally be pole mounted.

  2. The layout of the distribution transformers shall generally conform to relevant Construction Standards of Rural Electricity Corporation Ltd. and provisions in Indian Electricity Rules, 1956. The Licensee may adopt more improved layout for urban areas as per project report.

  3. The distribution transformers shall be located as close to the load centres as possible. Transformers above 100 KVA capacity other than those meant for indoor installations shall be outdoor plinth mounted with space for installation of a second Transformer.

  4. Moulded Case Circuit Breakers or Air Break Switches of suitable ratings shall be provided on the secondary side of transformers of capacity above 100 KVA for protecting the transformers from over load and short circuits. Fuse units of suitable ratings shall be provided on the secondary side of transformers of capacity up to and including 100 KVA for protecting the transformers from overload and short circuits.

4.3.2.5 11/0.23kV 1-phase Distribution Transformers (up to 16KVA Capacity.)
These transformers shall be pole mounted complying with provisions in Indian Electricity Rules, 1956 for isolating the transformer during overload and short circuit conditions.

4.3.3 Design Criteria for Distribution lines:
These criteria shall apply to all distribution lines up to and including 33kV for both overhead lines and under ground cables.

4.3.3.1 The lines shall be designed and constructed in accordance with relevant provision of I.E. Rule 1956 applicable to overhead lines and under-ground cables.

4.3.3.2 The distribution network fed from 11/0.4kV transformers and 33/11kV transformers shall be initially planned as independent networks within their respective service area. A service area of any particular substation shall mean for this purpose, an area, load in which shall normally be supplied by that sub- station by one or more number of feeders, as required, without exceeding the specified KVA-KM Loading limit of any feeder within the area.

4.3.3.4 The Licensee shall take suitable measures, sufficiently in advance, to augment the capacity of the feeders in the event of the specified KVA-KM Loading of any feeder being exceeded.

4.3.3.5 The design of the distribution lines shall incorporate features to enable their augmentation, in future, with minimum interruption to power supply. The existing Rights of Way shall be fully exploited.

4.3.3.6 KVA-KM Loading limits for conductors may be calculated in accordance with a sample calculation shown at Annexure-I.

4.3.4 Capacitive Reactance compensation:
Shunt capacitors unswitched/switched type, shall be installed in the Distribution System at suitable location for improvement of Power Factor, voltage profile and reduction of transmission and distribution losses. The size and location of capacitor installations shall be determined on the basis of reliable field data to avoid over voltages at light load periods. (Useful formulae are given in the Annexure-II which may be applied for determining approximate size and location of capacitor installations). The Licensee shall, however, undertake optimisation study of shunt compensation to determine most appropriate sizes and locations for shunt capacitor installations in comparision to other alternatives.

4.3.5 Service lines:
The service Wires to consumers shall be laid in accordance with relevant Construction Standards of Rural Electrification Corporation Ltd. for 230V/400V supply and shall conform to provision in Indian Electricity Rules, 1956 in all cases.

4.3.6 Metering Installations:
For 230V/400V the layout of metering installation shall be in accordance with relevant construction standards of Rural Electrification Corporation Ltd. The meters and associated metering equipment including connections shall be enclosed in a suitable tamper proof box. The tamper proof box shall be of sufficient strength and design with locking and sealing devices and with adequate provision for heat dissipation and electrical clearances. The design shall permit readings to be taken without access to the meter or its connections.
For HT and EHT Consumers the meters, maximum demand indicators, secondary connections, and other secondary apparatus and connections required shall be housed in a separate metering panel, which shall be locked/sealed to prevent tampering.Go Top

 

4.4 Security Standards:
The Licensee's Distribution System shall be planned and maintained so as to fulfill the following security standards except under Force Majeur Conditions beyond the reasonable control of the licensee.

  1. Loading in any current carrying component of the Distribution System (e.g. Conductors, Joints, Transformer, Switchgear, Cables, other apparatus etc.) shall not exceed 80% of the respective thermal limit.

  2. In case of single contingency failure in or to any 33/11kV sub-station excluding equipment, controlling any outgoing 11KV Feeders, the load interrupted shall not generally exceed 50% of the total demand on the sub-station. The licensee has to bring it down to 20% within a period of three years.

  3. In case of breakdown of any 33/0.4kV or 11/0.4kV Distribution sub-station,the electricity supply shall not be interrupted for more than 24 (Twenty four) hours except in case of major failures involving Transformers, the interruption shall not be for more than 7 (seven) days.

  4. In case of a failure in any 11KV Feeder including its terminal equipment, supply shall not normally be interrupted for more than 24 (Twenty four) hours but in no case shall exceed 7 (seven) days.

  5. There shall be at least two numbers of Transformers in each 33/11kV Sub-station.

  6. In each 33/11kV sub-station of capacity 10 MVA and above there shall be at least two incoming circuits.Go Top

 

5. OPERATING STANDARDS

5.1 General:
These Operating Standards are aimed at operating the Licensee's Distribution System safely, efficiently and to ensure maximum system stability and security.Go Top

 

5.2 Operation Criteria:
The operation criteria comprise of :

  1. Load monitoring and balancing

  2. Voltage monitoring and control

  3. Interruption Monitoring

  4. Data Logging

  5. Load management

  6. Communication

  7. Safety co-ordination

5.2.1.1 Load monitoring:
Licensee shall prescribe Rules and methods in its Operation manuals for monitoring load at the following places.

  1. 33/11 kV Sub-stations

  2. 33 kV Feeders

  3. 11 kV Feeders

  4. 11/0.4 kV Sub-stations (in all phases on the secondary side)

5.2.1.2 Load Balancing:
The unbalance of load between Phases in low tension distribution network fed by 33/0.4kV and 11/0.4 kV distribution transformers shall not exceed 5% (five percent) of the average load.

5.2.2 Voltage Monitoring and Control

5.2.2.1 Voltage monitoring at each 33/11 kV Sub-station shall be carried out by data logging.

5.2.2.2 Voltage monitoring on the secondary side of 33/0.4kV and 11/0.4kV distribution transformers shall be carried out at least once in one year during Peak Load hours to cover at least two nos. of transformers in each 11KV feeder as follows:

  1. One transformer towards the beginning of the feeder

  2. One transformer towards the end of the feeder

5.2.2.3 Improvement to voltage conditions shall be achieved by operating ON LOAD TAP CHANGE CONTROL of transformers in the Distribution System where such facility exists. The Licensee shall contact over Telephone the operators of Transmission and Bulk Supply Licensee at the point of interconnection, to correct voltage at the sending end as required.

5.2.3 INTERRUPTION MONITORING

5.2.3.1 Licensee shall maintain accurate record of consumer interruption caused by

(a) Planned and unplanned outages of following equipments in the Distribution System.

  1. 33KV line/equipments

  2. 33/11 KV Sub-Stations

  3. 11 KV line/equipments

  4. 11/0.4KV Sub-Stations

or

(b) Outage of power supply from interconnection points with GRIDCO or other power supplier

Each record shall contain at least the following information:

  1. Name of Section, Sub-Division and Division

  2. location

  3. Area affected

  4. The name of affected lines/ Sub-Station/ equipments/ Interconnection point (i.e. with Gridco or other power supplier)

  5. The date and time of interruption

  6. The date and time of restoration

  7. The duration of interruption

  8. The cause of interruption

  9. Whether the interruption is planned or unplanned

  10. The protection device if any operated/not operated

  11. Action taken for restoration of supply

  12. Preventive action if any taken

  13. Weather condition

  14. Damage/injury to property/life if any

5.2.3.2 Based on the above records, the Licensee is required to evaluate and monitor electricity supply reliability indices as stated in "Statement of System Performance" appended at the end of this document.

5.2.4 Data Logging:
All important data such as Voltage, Current, Power Factor, KWH, Transformer operational data (e.g. Tap position, oil/winding Temperature, etc) shall be logged on hourly basis in all 33/11kV sub-stations with installed capacity of 10 MVA and above and all other attended sub-stations.

5.2.5 Load Management:

5.2.5.1 In the event of total or partial black outs of Transmission System or Regional System the Licensee shall follow procedures as laid down in the GRID CODE under the Section contingency planning.

5.2.5.2 In the event of breakdown within its own System, the Licensee shall restore/maintain supply within the limit specified under security standards (Sub Section 4.4) by taking appropriate measures.

5.2.6 Communication:
The Licensee shall establish reliable communication facilities at its major 33/11kV sub-stations (10 MVA and above). All operating instructions, messages and data received from or sent to the concerned Grid Sub-station/Grid Substations and SLDC shall be duly recorded at such sub-station.

5.2.7 Safety Coordination:

5.2.7.1 The Licensee and consumers shall abide by the general safety requirements of the I.E.Rules 1956 for construction, installation, protection, operation and maintenance of electric supply lines and apparatus.

5.2.7.2 Procedures laid down in the relevant section of the grid code and distribution code shall be followed by the Licensee and its consumers, in this regard.

5.2.7.3 The Licensee and its consumers shall abide by provisions of I.E. Rules, 1956 under Chapter VII. "Electric supply lines, Systems and Apparatus for High and Extra High Voltages."

5.2.7.4 The Licensee shall develop its own Safety Manual to satisfy requirements of I.E. Rules and implement the same.Go Top

 

ANNEXURE-I

KVA-KM LOADING
( SAMPLE CALCULATIONS )

1. Conductor Data

Conductor Size --------------------------------------(6/3.35mm + 1/3.35mm)ACSR

Gross Area of Aluminium--------------------------52.95mm2

Copper Equivalent-----------------------------------32.26mm2

Resistance in ohms per KM (at 20C)------------0.5449*

Inductive reactance at 50 Hz in ohms per KM---0.421*
(For equivalent spacing of 1000mm)

* Appropriate values may be taken for any other temperature and equivalent spacing.

2. Assumptions

Length of line-------------------------1 KM

KVA loading--------------------------1000 KVA

3 phase voltage-----------------------11,000 V

3. Regulation

Percent Regulation (approx) = {I (R cos + X sine ) / E } x 100

Where

I = Current per phase in amp
R = Resistance per phase in ohms
X = Reactance per phase in ohms
Cos = Power Factor
E = Phase-Neutral voltage in volts

Percent Regulation = {48.2 (0.5449 x 0.8 + 0.421 x 0.6) / 6351} x 100 = 0.523%

For 1% Voltage Regulation the KVA-KM loading for the selected conductor size at 0.8 PF will be 1912 KVA-KM. For any other Power Factor, voltage and conductor temperature the Voltage Regulation may be calculated by substituting appropriate values of current, Resistance Cos and Sine in the formula. Go Top

 

 

ANNEXURE-II

SHUNT CAPACITOR INSTALLATION
(USEFUL FORMULAE)

1. Capacitor Required

KVAR = KVA1 (Sin 1 – [Cos 1 / Cos 2] . Sin 2)

Where KVAR is : amount of capacitance to be added to improve the Power Factor from Cos 1 to Cos 2.

KVA1 is : Original KVA.

2. Optimum location of capacitors

L = [1 – (KVARC / 2 KVARL) x (2n-1)]

Where,

L = distance in per unit along the line from sub-station
KVARC = Size of capacitor bank
KVARL = KVAR loading of line
n = relative position of capacitor bank along the feeder from sub-station if the total capacitance is to be divided into more than one Bank along the line. If all capacitance is put in one Bank than values of n=1.

3. Voltage Rise due to Capacitor installation

% Rise = (KVARC.X) / 10V2

Where,

X = Reactance per phase
V = Phase to phase voltage in kilovoltsGo Top

 

STATEMENT OF SYSTEM PERFORMANCE

Ref:- Condition 20.2 read with Condition 20.4 of Distribution and Retail Supply Licence

A quarterly report on performance of the system, with reference to the operating standard shall be submitted to OERC within 25 days of end of each quarter i.e., by 25th of April, July, October and January each year. An annual report on the year ending 31st March shall be submitted by 25th April along with the report on the first quarter report. The report on the electricity supply reliability indices shall contain the following information :

a) "SAIDI" or the System Average Interruption Duration Index : This represents the average time each consumers is interrupted. SAIDI is expressed by the following formula :

SAIDI = Sum of consumer interruption durations / Total number of consumers served

b) "SAIFI" or the System Average Interruption Frequency Index : This represents the average number of interruptions per consumer SAIFI is expressed by the following formula :

SAIFI = Total number of consumer interruptions / Total number of consumer served

c) "CAIDI" or the Customer Average Interruption Duration Index : This represents the average interruption duration or average time to restore service per interrupted consumer CAIDI is expressed by the following formula :

CAIDI = Sum of consumer interruption durations / Total Number of consumer interruptions = SAIDI / SAIFIGo Top