Guidelines to be followed by the various executing agencies in planning the future augmentation/additions to generating capacities and transmission system.

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Unified Load Dispatch and Communication Schemes
Augmentation Required Under Future Projects

Introduction

The Unified Load Dispatch Schemes finalized for Southern, Northern and North Eastern Regions Have taken into account the system additions upto the Year 2000 A.D. would have to be provided with data acquisition facilities to enable their integration into the proposed Unified schemes.

In this approach paper the guidelines to be followed by the various executing agencies in planning he future augmentation/additions to generating capacities and transmission system have been set forth so that the 'Regional Interest' Sub stations and Power plants planned in the future form part of the proposed unified load dispatch scheme.

Facilities under Control

Regional Interest Substations/Power Stations

Only the facilities of Regional Interest i.e. participating significantly in the regional integrated operation of the grid will be covered by the unified scheme.

Consequently the facilities under control include:

All generating stations of 50 MW and above.
(10 MW and above in the case of North Eastern Region)
All 400 KV Sub-Stations.
All 220 KV Sub-Stations.
All 132 KV Sub-Stations operated in closed loop or Where inter-state tie lines are located.
Important 66 KV Sub-Stations. (In the case of NER only)

If the proposed facilities fall into any of the categories listed above the agency formulating the scheme must coordinate with CEA and make sufficient provisions in their project report to the satisfaction of CEA so that the tele-information plan is in conformity with requirement of the Unified Scheme. CEA's clearance, must be subject to the proposed scheme complying with tele-information requirements of the Unified Load Dispatch scheme.

The ownership of equipments

The equipments necessary for the integration of the proposed scheme with the Unified load dispatch scheme comprises of the following.
Part-I: Data Acquisition Transmission Equipments

Acquisition Work in the Substation & Power Plants
Remote Terminal Unit
PLCC carrier sets, coupling Devices and CV

Part-II: Augmentation of the existing facilities under the Unified scheme

Augmentation of the communication system of Unified load dispatch scheme
Augmentation of the Computers/Processors.

The proposed Power plant/Transmission System may be executed and owned by any of the following agencies :

Constituent SEBs/ Electricity Depts. of
of the concerned region.
A Licensee company
Central Sector undertaking
A private sector Generating Company.
POWERGRID

In each of the above cases the equipments necessary for Data Acquisition/ Data Transmission (Part-I) would be owned by the respective agency/Central Sector undertaking.The equipments under Part-II viz. Augmentation of the Communication/ Computer would need to be done by the Constituent SEB/Electricity Dept. concerned. Where the would proposed Power Plant/Transmission System is owned by a Central Sector agency, the augmentation of CPCC and RSCC would be carried out by POWERGRID. It may be relevant here to point out that the augmentation of the Communication system is required where the communication from/to the Sub LDC does not have the necessary channel capacity of the substation is located in a remote place that it can not be covered by a nearby sub LDC. The augmentation of the computing facilities at RSCC/SLDC/Sub-LDC however would be necessary only when the system undergoes a massive expansion.

Scope of Works

The equipments necessary to be provided by the concerned executing agency pertain to the following:

The Data acquisition/Transmission equipments.
The Communication equipments.

Data Acquisition Transmission equipments
- The Data acquisition principles
  The data to be measured/collected include Voltage, Current Power both active and reactive Frequency, Breakers' Isolators status and Transformer tap position. The data receiving concept in real time mode proposed in the present scheme is that data from Remote Terminal Units (RTUs) located in substations generating, stations would flow sub-LDC's, CPCCs.The detailed data acquisition principles have been set out in Annexure-1A.
- Adaptation works substations
  The adaptation work in substations includes all supply/installation work to interface the prop installations up to the Remote Terminal Unit, in particular.
  The following transducers:
  -Active Power P
  -Reactive Power Q
  -Current I
  -Voltage V
  -frequency F
  -OLTC position
  -Decoupling relays:
  -Interface cubicles:
  -Wires and cables to connect all these new equipment.
- Adaptation work in power stations
  The adaptation work in power stations comprises of two main parts:Interfacing of signals not available in the substation but necessary for system operation such as gross active or reactive power, reservoir levels etc. Basically, the scope of work/supply is similar to that describer for substations.The hardware at generating stations for Automatic Generation Control is not being implemented presently as part of the Unified scheme. The hardware necessary for LFC would have to be implemented by power stations of capacity of more than 50 MW as and when the same is implemented on the Regional level.
- Data Transmission Equipment
  The data to be provided to the SLDC is transmitted to the Sub LDC by the RTU of the concerned substation/power station, from where the same is transmitted over high capacity Microwave/Fibre Optic links. In the case of CPCC the data from an RTU flows directly to the CPCC. Given below are some of the salient features of the data transmission equipment Viz. RTU.4.1.5 Characteristics of the RTUThe Communication protocol of the RTU must conform to the protocol incorporated in the unified scheme.
  - The RTU must be equipped with two Modems.
  - The RTU shall be capable of accepting:
    - Single Point/Double Point Information indication signals.
    - The RTU's will accept tele-measuring signals under the form of DC signals.
  - Single Point/Double point digital controls.
  - The RTU must be capable of time tagging the status changes with a 10 ms resolutions.

The Communication Equipment
The communication between RTUs and Sub-LDC is based on PLCC. The data from the proposed new substations and power stations would flow to the nearest Sub-LDC in the case of state sector/private sector facilities. In the case of central sector facilities or private sector facilities conceived as 'Regional' facilities the data would flow to the nearest CPCC.
The communication facilities shall be designed to meet the requirements of data, speech, fax. etc. and be compatible with the facilities under the Unified Scheme.
D.C. System
48 Volt D.C. System of adequate capacity shall be designed to meet the power requirements of communication and tele-control equipment.
The 48 Volt D.C. System shall comprise of
-two rectifiers simultaneously operating in parallel and sharing the total current demand.
-One set of batteries.
-Suitable distribution board.

ANNEXURE-IA

PRINCIPLES OF DATA ACQUISITION

Sr. No.	Subject
1.1.	General The teleinformation plan corresponds to the requirements for data collection that will enable the carious levels of the power system control hierarchy to fulfill their role. That means in particular that apparatus statuses like bus selector disconnector position, and alarms like loss voltage are considered and that some circuit breakers remote control facilities are planned.
1.2	Data Transmission principles The circuit breaker positions are collected under the shape of double signals (D S) as this is necessary if remote control functions are considered (immediately or in the future), and as it is more reliable for the network state estimation. As far as isolator positions are concerned it seems that the need for remote control of this kind of apparatus is not necessary at least in the near future. Thus, it was decided that only Single signal are chosen for isolators. Of course, for a better accuracy of the information relating to the knowledge of the system and for state estimation, it should have been better to choose double signals but for economy reasons, single signals have been prefered. For all the apparatus positions, the information will be transmitted when a change as status occurs. The same applies for the OLTC position. All the possible alarms are collected under the shape of single signals. For all analog values, they are cyclically transmitted. A reasonable cycle time has been chosen for all the most important values concerning active and reactive power, voltage....., i.e. 10 seconds. For the current measurements on apparatuses located at a low voltage level (transformers or feeders at 66 kV or 33 kV), a cycle of 30s is sufficient.
1.3	Principles for data acquistion
1.3.1	Busbar section a) Voltage: - 400, 220 and 132 kV : one value per main bus bar. - 66 kV: one value per station. - 33 kV: no value. b) Frequency: - 400 KV: one value per main busbar - 220 KV: one value per station expect for stations where power units are connected or having inter state feeders (2 value :one per main busbar) - 132/66KV : one value per station where power units are connected to 220KV stations c) S S : - I S S for loss of voltage per busbar (busbar disconnectors are counted separately hereafter).
1.3.2	Bus bar coupler D S: 1 D S per circuit breaker. S S: 1 S S for only one out of the 2 disconnectors.
1.3.3	Bus Transfer D S : 1 D S per circuit breaker. S S : 1 S S for each disconnector on both sides of the C B.
1.3.4	Bus bar Disconnector S S : 1 S S for each bus bar disconnector (whatever the voltage level) and including bus bar transfer.
1.3.5	Capacitor D S : 1 D S per circuit breaker. S S : 1 S S for each bus selector disconnector.
1.3.6	Reactor connected to busbar and synchronous compensator. a) Reactive power : 1 value. b) D S : 1 D S per circuit breaker. c) S S : 1 S S for each bus selector disconnector in case of single breaker arrangement. 1 S S for each disconnector in case of one-hand-half breaker arrangement (3 disconnectors per bus bar connection).
1.3.7	Gas generator and Hydroelectric Generator (substation side) Active power : 1 value. Reactive power : 1 value. D S : - 1 D S per substation circuit-breaker - 1 D S per generator bus coupler S S : - 1 S S for each bus selector disconnector in case of single breaker arrangement (Including bus bar transfer). - 1 S S for each disconnector in case of one-and-half breaker arrangement: (3 disconnetors per bus bar connection). Single bit indication Double bit indication - 1 S S for cach by-pass disconnector in case of single breaker + by-pass arrangement. Reservoir level : 1 value per hydro station when it is already available on site.
1.3.8	Thermal Generator (substation side) In addition to the above mentioned data for gas generator, 2 other data pertaining to auxiliaries must be added: - one value of P for gross active output, - one value of Q for gross reactive output.
1.3.9	Remote generator In case power plant needs its own RTU because of the distance to the substation, connections in the corresponding substation are to be described as overhead line connection and remote generators as follows: - 1 D S per circuit-breaker (if existing for out-going feeder), - 1 D S per generator bus coupler, - one value of P for gross active output of a thermal generator, one value of Q for gross reactive output of thermal generator.
1.3.10	Overhead line a) Active power and reactive power - 400, 220 and 132 kV: one value of P and Q for each outgoing line, - 66 kV: one value of P and Q only for outgoing inter-systems tie-line, - 33 kV: no value. b) D S For each 400, 220 and 132 kV outgoing line and 66 kV outgoing tie-line: - 1 D S per substation circuit-breaker - 1 D S per reactor disconnector (or circuit-breaker in the future) connecting it to the 400 kV line. c) S S For each 400, 220 and 132 kV outgoing line and 66 kV outgoing tie-line: - 1 S S for each bus selector disconnector in case of single breaker arrangement. - 1 S S for each disconnector in case of one-and-half breaker arrangement (3 disconnectors for each outgoing line). For each by pass disconnector in case of single breaker + by-pass arrangement. d) DC - 1 D C for each 132 kV outgoing line. The choice consisting in the implementation of remote control only for 132 kV feeders and below can be justified by the needs of quick switching operation requirements for load shedding and emergency actions. In some particular cases, some remote control facilities may be interesting also for 220 kV or 400 kV components of the grid. These specific requirements shall be precisely defined at technical specification drafting stage.
1.3.11	Transformers a) Active Power and Reactive Power One value of P and one value of Q measured on the secondary level for 400 kV/220 kV or 220/132 kV transformers, or on the primary level for the 132/66, 132/33 or 132/11kV transformer. If the secondary level doesn't belong to the same Constituent as the primary level. P and Q are measured on the primary level (case of Central Sectors). b) Current (for secondary side of 132 kV regional interest substations) One current value (1) measured on the primary level for the 66/33 kV, 66/22 kV 66/11 kV or 33/11 kV transformers. c) OLTC The position of each On load Tap Changer is indicated with a digital or analog tele-measuring. This shall be precisely defined for each individual case at specification stage. d) D S 1 D S per circuit-breaker. If the secondary level doesn't belong to the same network (case of Central Sectors), 1 D S shall also be collected for the secondary circuit-breaker. e) S S - 1 S S for each bus selector disconnector in case of single breaker arrangement. - 1 S S for each disconnector in case of one and half breaker arrangement (disconnectors per bus bar connection). - 1 S S for each by pass disconnector in case of single breaker +by- pass arrangement: DC for secondary side of 132 KV regional innerest substations Secondary level for the 132 KV and 66KV transformers Single bit centrel