Introduction and overview
The Cashpower Power-Rail is a single-phase 60A (80A optional) split meter in a DIN rail-mount
housing. Ideal for new reticulation where housing is informal and the prepayment
meters are mounted in a pole-top enclosure with respective customer interface units
conveniently mounted in the dwellings below. Due to the small size and DIN rail
housing, multiple Power-Rail meters can be mounted in a small enclosure thereby
making installation cost effective
Features
- Compact meter design, with DIN rail-mount layout for high density stacking
- Easy to install Customer Interface Unit provides valuable information to help consumers
effectively manage their electricity consumption
- Galvanically isolated communication link to customer interface unit for consumer
safety
- Plug-in communications connector on the meter for easier utility access and maintenance
- Programmable operating mode - Energy Limiting Mode, Prepayment or Credit metering
- Programmable software power limit
- Programmable monthly allocation of energy (MAE)
- Commissioning and de-commissioning feature
- Significant Reverse Energy (SRE) detection
- Meter state indication LED and communication diagnostic LED at the meter
- High surge withstand capability for areas prone to lightning or other line surges
- High temperature withstand capability
- SABS 1524 and IEC 62052-11, IEC 62053-21 compliant
Split meter concept
The Cashpower Power-Rail consists of two parts: the Customer Interface Unit and the Meter. The
Customer Interface Unit is a compact unit with userfriendly display and keypad that
can be installed in any convenient location inside the consumer’s premises. Connection
to the remotely installed meter is via a pair of communications wires. The connection
of these wires at the meter is achieved by means of a plug-in connector, facilitating
easy installation and maintenance. The meter contains all critical metering, number
decryption and load control functionality. It operates independently of the customer
interface unit and is immune to any form of tampering on the customer interface.
The meter is usually installed in a secure, locked enclosure - typically a pavement
kiosk or polemounted equivalent. It is outside the consumer’s premises to facilitate
easy inspection by the utility at any time, thus reducing the possibility of tampering.
Principle of operation
The Cashpower Power-Rail meter in the Energy Limiting Mode, provides utilities with the utmost
flexibility in terms of being able to adapt to a range of different consumer profiles.
Three, utility-programmable modes of operation are available and it is possible
to switch between modes as required:
Energy Limiting Mode
This mode allows utilities to distribute a fixed, monthly allocation of energy to
consumers. It encourages the rational use of energy without severely inconveniencing
the consumer. Operation is as follows: Assume that a monthly energy allowance of
150kWh has been allocated to a consumer. The meter allocates this energy in regular,
equal portions, over the thirty-day period i.e. by incrementing the kWh credit level
with a value of 0.00087kWh every 15 seconds. Assuming that the consumer draws no
power at all, the credit level will continue to increase. However, as soon as energy
starts to be used, the credit level is proportionately decremented. If the rate
at which energy is being used is less than the rate at which it is being incremented,
the credit level will slowly continue to increase. If the rate at which energy is
being used is greater than the rate at which it is being incremented, the credit
level will slowly decrease. It is in the consumer’s interest to ensure that electricity
is not wasted and that unnecessary appliances are turned off. By conserving energy,
it will be possible to use it at a high rate for periods when required. In the event
of the consumer exceeding the allocated allowance (credit level reduced to zero),
the load is disconnected. However, the next allocation of credit will be available
within a very short period of time (15 seconds) and the supply of electricity restored.
Providing the consumer takes immediate steps to disconnect unnecessary appliances,
it will be possible to have at least basic services available e.g. lighting. With
a 150kWh monthly allocation of energy, it will be possible to maintain a continuous
load of 200W whilst still maintaining a positive credit balance.
Prepayment mode
In Prepayment metering mode, it functions as a normal prepayment meter. Credit tokens
are purchased and entered into the meter via the customer interface unit keypad.
On expiry of credit, the load is disconnected and will only be re-connected when
a valid credit token, purchased by the consumer, is entered.
Credit mode
In Credit metering mode, it functions as a conventional credit meter. Power is continuously
supplied to the consumer and total kWh used is continuously measured and recorded.
The meter must be read by the utility at regular intervals and the consumer billed
accordingly.
Automatic / manual supply re-connection
A programmable function allows for either automatic or manual restoration of power
to the load after it has been disconnected for a period due to expiry of credit
or Power Limiting. Manual restoration is accomplished via the customer interface
unit.
User-friendly customer interface
The meter is controlled via the CIU in exactly the same way as other meters in the
meter range. User interaction with the meter, and access to meter information e.g.
rate of energy consumption, low credit warning and load contactor status is available
using the customer Interface’s keypad and large LCD. The customer Interface Unit
makes use of clear, languageindependent icons. The user interface is further enhanced
by the use of audible tones. These are sounded under different conditions e.g. Low
Credit Alarm and Token Accept.
Meter status and diagnostic indicators
The meter includes an LED status indicator. This allows a technician to view the
state of the meter without the need for specialised interrogation tools or having
to gain access to the consumer’s premises. Information such as Tamper status, Power
Limiting, Commissioned/Decommissioned status and Remaining Credit status are available.
The meter also features a dedicated diagnostic LED for the Customer Interface. It
can indicate the presence of "Open" or "Short" circuited communication lines. This
is a valuable visual aid that assists the technician to validate the installation
and determine probable fault types.
Interrogation port
As a customer option, more detailed information and programming is achieved via
the standard interrogation port on the side of the meter.
Optical interface
As a standard feature, the meter has an IEC 62056-21 compliant optical communications
port. This allows the utility to access a variety of information stored inside the
meter, and to upload it to a hand-held unit.
Tamper detection
The split configuration of the meter significantly reduces the risk of tampering.
The meter is installed in a remote, secure location and is mechanically sealed against
tampering through the use mechanical clips and inaccessible assembly screws. Utility-sealed
wire seals can be field-fitted to secure the main power cable terminations. The
use of these mechanical seals ensures that there will be visible signs of tampering
if unauthorised entry to the system is attempted. The meter also has a feature allowing
detection of Significant Reverse Energy (SRE). If the line and load wires are swapped
during installation, the meter will continue to operate and decrement credit. The
unit may be factory programmed to Tamper and disconnect the consumer’s load should
SRE be detected.
Disconnect on Power Fail
The meter includes a feature to cater for a condition where the neutral link to
the device is removed. The meter can be personalised to disconnect the load if a
power failure is detected, as would be the case if the neutral wire were to be removed.
Surge protection
The meter has been designed to have a surge voltage withstand that significantly
exceeds the requirements of both SABS 1524 and IEC 62052-11. Depending on the installation’s
electrical environment, the customer has the option of fitting an additional surge
arrestor with a current surge rating in excess of 30kA.
Installation features
The meter is suited for connection to most metering and reticulation systems. The
communication wires for the customer interface are non-polarised and safety-isolated.
This simplifies the installation process and also ensures safety within the consumer’s
premises. The communication wires can be included as separate cores in a concentric
reticulation cable and provide a very robust communications interface between the
meter and the customer interface over a distance of at least 130 metres.
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