Revenue Protection and Technoloy Intervention in Metering,Billin and Collection

The power supply industry has reached an impasse where urgent steps are required to improve the financial health of the utilities. The revenue to the power utilities can be increased only if it can be ensured that the power sold by them is first of all accounted for, billed for and payments collected in time.There is a greater focus now in the electricity utilities to improve their revenue management system. A large number of meters installed are either defective or stopped. These need to be replaced. The existing meters are tampered to a large extent. The metering device should have capability of recording tampering with its identification and profiling at the time of tampering.Solutions to the limitations and inadequacies of the present metering system can be provided through emerging electronic power metering technologies such as electronic meters, prepaid meters and remote metering.

In addition, the existing system of meter reading and billing is cumbersome and requires a huge workforce to serve a large customer base. The system of a two month billing cycle and the time lag between reading of meter and subsequent preparation, delivery and payment of bills, results in delayed benefit realization by the utility. Non-payment and delay in payments further aggravates the situation for the utility, with the utility having no option but to continue supplying power except in certain extreme cases. Frequent court cases/ public interest litigation cases on account of faulty billing are also causing concern to utility and harassment to the consumers.

Accuracy of bills can be improved by implementing better metering technologies, taking accurate readings by avoiding manual intervention and automating the billing process. The best practices for improving billing accuracy are described in Box

Box : Best Practices for Improved Billing Accuracy
• Download devices for meter reading

• Meter reading interface with billing applications

• Computerized Billing for computation and dispatch of the bill

• Spot billing

Collection and Payment Systems

Payments are currently made in person in most of the places. Only in few places payments can be made on line or through the ATM (Automated Teller Machine). Power utilities can use IT (Information Technology) applications for payment, such as• Electronic payments, including direct debit payments

• Prepaid metering

• Bar coding facility, even when payment is made in person, for faster payment

• Multiple payment locations and not restricted to a particular division subdivision

For providing electronic payment, use of IT would be required for providing interface with entities like banks and building Internet based payment processing. At present, power utilities allow only full payment and the system for providing part payment is minimal or does not exist. This could be introduced by the power utilities.

Revenue protection is highly dependent on the reports generated for MIS(Management Information System) viz. Reports of consumption rise or drop more than 20%, list of consumers with irregular payment, consumption below norms etc. The vigilance department should use these details to take action against erring consumers.

Meter Field Testing and Installation Practices

In this section, we discuss the installation, commissioning and field testing of meters.

Energy Meters – Installation and Commissioning

The meters are connected before the consumer’s isolating device (Main Switch), which may be a moulded case circuit breaker, miniature circuit breaker or an ironclad switch fuse unit. At the time of commissioning, each meter is tested at site by the owner. A reference standard meter of 0.2 class or better is used for testing.

Supply Side Wiring

The supply side wiring is the responsibility of the utility and the following must be ensured while carrying it out:

a) The supply wires provided are of suitable rating.

b) In case of more than one meter on one service line, it is preferable to use bus-bars. When a number of meters are connected to single distributing mains for registering electricity supplied to different consumer loads,separate service lines – phase(s) and neutral, are used for each meter.Each independently metered consumer load is directly connected to distributing mains through its meter connected in specified phase sequence so as to meet accuracy requirements of relevant standard.

c) The supply wire is properly terminated.

d) The connection is as per connection diagram mentioned on meter.

e) Utility should use its own earthing for its devices.

Utility provides phase and neutral supply to the consumers. The neutral is used for carrying return current only. The neutral of one consumer should not be connected to other consumers who have independent and separate supply connection. Utility provides separate neutral to each consumer up the metering point and same is used by the consumer. The consumer ensures that all the correct wiring practices are followed and neutral is not looped with another consumer or meters in the same premises. Consumer should not earth the neutral after the metering point. Wherever there is multiple metern installations, bus bar arrangement is used for neutral, so that looping is avoided.

Installation of Meters and Verification of Connections

Apart from testing and calibrating the meters they must be properly installed as per the connection diagram. The points that must be kept in view while meters are installed are given in Box .

Box : Installation of Meters

a) Position of meter should be such that reading is easily visible.

b) Mounting of meter should be on solid wall or DP structure or on panel board.

c) Vertical mounting of meters should be ensured. The utility engineer should use a plumb bob and mark a vertical line prior to installation.He could also use a spirit level and put on the top of the meter after hanging on the screw hole. Alternatively, he should put spirit level on the edge of the terminal block to ensure vertical mounting.

d) For HT metering equipment, CTs should be right on the incoming side before the point of isolation.

e) The meter box should be sealed.

f)The meter recording should be checked at site.

The following should also be ensured:

a) Appropriate crimping device should be used for crimping the lugs.Thimbles should be of appropriate configuration (pin type, fork type etc.) to match with the terminal block for low current connection. For high current terminations, crimping should be used with cable crimping tools and multiple point crimping should be done for the lugs used for higher current ratings.

b) If the terminal block is of MS cage clamp type, there is no need to use any lugs and the copper cables can be directly terminated at the clamp.

c) The recommended tightening torque must be exerted on the screw to ensure proper tightening of the terminations. It is recommended to use proper tools, equipments for this purpose.

d) Usage of lugs as per the recommendation of manufacturer and ensuring proper crimping will protect the joints from failures.

e) For high current terminations, tensile test and shock test should be performed after crimping the lugs.

f)Where aluminium cable termination is to be done on copper bus bars or brass studs, bimetallic type of lugs should be used.

g) Some meters have lower terminal pitch. Because of this, cables foul with each other while installation. Proper cable size according to the meter rating should be defined.

h) Aluminium conductor cables should be replaced by copper cables for the whole current meters.

i)For indoor meters, the wiring should be done such that the cables enter the meter box from the bottom or rear side. This not only is aesthetic, but also prevents the service cable from tampers, etc.

The points that should be verified after installation of the metering system are given in Box.

Box : Points of Verification

i) Phase association

ii) CT polarity

iii) VT polarity

iv) Phase angles

v) Phase sequence

vi) System conditions – unbalanced capacitors

vii) Actual CT / VT ratio

Sealing Points

The meter seal should be tamper proof. The consumer should be briefed about seals. The sealing of all metering systems should be done at various points (as applicable) to avoid tampering. There should be at least one seal at all points mentioned below (wherever applicable):

a) CT Secondary Boxes (in addition to locking arrangement)

b) PT Secondary Box (in addition to the locking arrangement)

c) Meter Cabinet

d) Meter Test Block

e) Meter Terminal Cover

f)Meter Cover

g) Panel doors where CT and PT secondary circuits are terminated or where possibility for shorting or breaking exists and fuses/links are provided.

h) PT selector relay box where automatic change-over of potential supply to meter from one PT to another is provided

i) CT Primary Links and Top Covers

j) MD Reset Push Button

k) Boxes/Cabinets containing terminals for remote transmission of metered data via communication channels, junction boxes in the system and boxes wherein interface devices are mounted.

l)Meter reading port.Seals are necessary to guard against the tampering of connections and internal parts of a meter. Tampering of seals will give consumers access to th relevant part of a meter installation where s/he can manipulate the unit to record less energy leading to commercial loss. A seal is placed to detect unauthorized entry to the meter internals.

The effectiveness of the seal depends on the type of seal (whether it is tamper proof or not, whether a duplicate can be obtained or not, etc.), and the procedures used in tracking the seals.

The important points for seal management are given in Box .

Box : Seal Management

For an effective seal management system it is essential that:

i)The seals used are tamper proof, i.e., they cannot be removed and replaced by customers.

ii) The seals should be from such sources that duplicates should not be available or cannot be manufactured.

iii) The number of seals placed on each meter should not be very large, as this will cause logistic problems in managing and auditing the seals.

iv) A proper seal issuing and managing system should be put into place where location of each seal can be traced at any point of time. This covers tracking its total movement starting from ordering,manufacturing, procurement, storage, record keeping, installation, series of inspection, removal and disposal.

v) Seals must be stored securely and assigned to individuals responsible for their safekeeping.

vi) Seal audits should be checked routinely, particularly at the time of meter reading and also through audit checks.

Calibratation and Testing of Energy Meters and Meters Laboratory

Energy meters form a vital instrument of revenue realization for the distribution utilities. Based on the meter reading, the utilities submit their bills to consumers for realization. Inaccurate/faulty recording may become catastrophic both to consumers and utilities. Thus, a need to ensure a high degree of performance and reliability from the meters has become important.The meters are tested and calibrated to ensure proper working and that the accuracy is to be maintained within permissible limits under IE Rules.As per Indian Standard specification 722, a meter should pass the following two types of tests:

• Type Tests

• Routine TestsMeters are calibrated such that the overall accuracy is within the percentage error limits. All initial calibrations of meters are performed in a laboratory or test house. The most common method for testing meters is to inject voltage and current from a stable power source in combination with a reference meter.

The main requirement in a test lab will be: Test bench, Reference standards, Power source, Software and Accessories.

Test Bench

 

The test bench could be for single phase or three phase meters,electromechanical or electronic. It could be fully automatic, semi automatic or manual. As per the Indian Electricity Rules, the meters in service need to keep to the prescribed accuracy range. With time the accuracy of the Ferrari’s meter degrades and the meter tends to slow down. For that, periodical testing of and recalibration of all meters installed in the field for all categories of consumers need to be carried out as per the meter standards. The test schedule as per the Central Electricity Authority Regulations on Installation and Operation of Meters is given in Table.

Test Schedule

Meter Type Schedule

The testing schedule for HT consumers should cover the entire Metering System including CTs, PTs and Pilot Wire. Detailed ratio testing of CT, PT and control Pilot/ wires is to be done. Testing through mobile vans/mobile cubicles through secondary injections kit and phantom loading may also be carried out by Measurement Unit. All new meters should meet the requirements of Accuracy Class spelt out in Table.

Requirements of Accuracy Class

Methods of Testing

Irrespective of purpose, testing is generally carried out

• on site, or

• in a Meter Testing Station (MTS) accredited as per IS/ISO/IEC 17025.

On-site testing may be carried out

i)under actual prevailing load; and

ii) by injection method after connecting a suitable phantom load or a resistive load.

i)Actual Loading Method
This method is employed generally for testing of single phase meters in laboratory. On a meter testing bench which is equipped with various taps to facilitate meter testing at different load conditions. The load is provided by standard resistance or lamps obviously power factor is unity. Load adjustments are done in steps of 1/10 th of full load at unity power factor.It is important to note in this connection that consumer’s power factor varies from 0.5 to unity (or 0.85). Therefore, meter must be calibrated at 0.5 PF. To achieve this condition, the current coil is energized by R phase and voltage coil by Y phase and the polarity of pressure coil is reversed.Under these conditions, PF becomes 0.5 because of 120 degree phase shift between voltage and current vectors.

ii) Phantom or Fictitious Loading Method
When the capacity of meters under test is very high, testing with actual load method would involve a considerable loss of power and would not beeconomical too. Therefore, to avoid wastage of power during testing,phantom load method is adopted. In this method, pressure circuit is supplied from a circuit of normal voltage source and the current circuit from a separate low voltage source. Thus, total power consumed during testing becomes very small due to small pressure coil current at normal voltage plus full load current at very less voltage for current circuit meter. However,the meter under test in this condition simulates the full load condition by such phantom load kit.

Testing of CT Operated Meters

The following tests should be carried out for CT operated meters:

i)Ratio test by primary injection kit,

ii) Polarity test,

iii) Continuity test of primary and secondary windings,

iv) Insulation resistance test, and

v) Terminal markings as per name plate details.

It should be noted that CT Secondary terminals should not be kept open. For CT and PT operated meters, it is preferable to use a Test Terminal Block(TTB). The TTB provides the facilities of shorting CT secondaries for testing purpose without any interruption to the consumer. The CT leads should be directly connected to the meter, while PT supply to the meter should be connected through the fuses of proper rating. To eliminate the possibility of tampering with the fuses, the fuses should be provided with protective cover and properly sealed.

Checking at Site

The routine testing of meters should be carried out once in 3 years. In addition, surprise checks should be conducted at the consumer’s installation and meters should be checked from time to time. The important points to be paid attention to while checking are given in Box .

Box : Checklist of Important Points for Checking at Site

i) Connections of meter are proper.

ii) Seals are not tampered with.

iii) No loose or direct connections exist.

iv) Meter is not damaged to record less.

v) CTs are properly connected. No reversal of any phase connection exists. Multiplying factor is properly calculated and applied.

vi) Meter is well protected from rain, vermin’s and dust etc.

vii) Links are connected.

viii) Terminal block is not damaged.

With the help of load current of known magnitude (preferably of resistive type) and a wrist watch having a second’s hand, you can off hand check at site the performance of the meter as also its accuracy to some extent.