Many industries have incorporated the 'just in time' philosophy to maximise production efficiencies. In the energy industry, which includes electricity, natural gas, steam, water and other piped commodities, there is a desire by energy producers and consumers for the integration of real-time pricing, energy consumption and billing anticipation at one consolidated observation point – the energy manager’s desk.

In the past, the limitations of older technologies have made this a very expensive and onerous objective. However, today’s multifunction electronic end-devices, together with the creative application of new metering and monitoring solutions, have equipped energy managers with powerful tools to better monitor and manage energy costs. Furthermore, these systems have allowed energy  consumers to earn revenue streams by being able to respond to market signals, dispatch instructions or other market mechanisms to shift or drop load at critical periods. Today’s energy and metering solutions providers are able to go beyond the meter with the smart deployment of new metering technologies. Smart deployment strategies enable the larger high voltage-connected electricity market participants such as local distribution companies (LDCs), transmitters, generators and large commercial and industrial (C&I) customers to benefit from the extensive non-revenue capabilities of today’s revenue meters in ways that complement their various business needs.

MANAGING CHANGE

Limitations of conventional revenue metering equipment and past design practices have traditionally forced designers to attach numerous discrete electromechanical and analogue devices to revenue current transformer (CT) and voltage transformer (VT) circuits, in order to provide the data demanded by a variety of stakeholders with differing interests. This type of design inevitably compromised instrument transformer (IT) accuracy due to higher burdens being imposed on the current and voltage transformer windings. The security of the metering circuit is also jeopardised by the increased number of exposed access points available to possible tampering. In addition, costly equipment and space are required to sustain the data flow. And finally, subject experts on these devices are required during the operation and maintenance portion of the equipment life-cycle. As these devices reach the end of their life, and the number of subject experts diminishes, the owner faces the dilemma of finding a like-for-like replacement or upgrading to new technologies that have a large suite of features on which to draw. Two changes in electricity markets are causing designers to re-think their approach to revenue metering:

1. The requirement by many regulators to have dedicated CTs and VTs for revenue meters, tamper-proof interconnections and lockable cabinets, often even disallowing the use of the second winding of a dualwinding VT by non-revenue devices, if outside the locked metering cabinet.

2. The increased capability of new revenue meters. They are now multifunction electronic end-devices (MEEDs) that typically have about 20% utilisation to support all revenue metering needs, allowing the owner to benefit from the untapped functionality of the other 80%.

DESIGN CHALLENGES

In order to have a level playing field for participants and to hold the market harmless, many independent system operators (ISOs) in deregulated electrical markets have produced standards that specify dedicated current (CT) and voltage (VT) transformers to ensure that accuracies are not compromised by unknown burdens. This presents a challenge to metering system designers when old nonconforming metering schemes must be upgraded to new standards, or abandoned and totally replaced at another physical location, while sustaining data needs from devices about to be purged from the revenue circuits. To meet this challenge today’s designer judiciously selects revenue meters with the MEED capability and applies 20% of the meter’s functionality towards the ISO’s mandatory requirements. The other 80% of the meter’s capabilities is customised around the client’s non-revenue needs. Customisation often involves integrating the meter with third party devices and protocols.

DEVELOPING A METERING SYSTEM ARCHITECTURE

The latest meters have a partitioned section (the 20% portion) that contains all the critical measurement devices and firmware. These areas are enabled with anti-tampering hardware/ software locks that can be sealed by a regulator to ensure compliant measurement over a defined period of time. Although these sealed internal devices are inaccessible to the normal user, their outputs and characteristics are available for non-revenue purposes (the 80% portion). Thus the ‘metering system architect’ can expand the meter’s remaining capability to suit a client’s many needs, selecting from a generous offering of features.

Local and/or remote access from various software platforms with multi-level password protection reflects the extent of secure access and user empowerment to modify a meter’s parameters. Powerful analytical capability for forensic power quality investigations, displacing expensive data loggers to:

- capture harmonic distortion incidents associated with disturbances;
- monitor generator or load performance with storage intervals in the seconds range; and
- program conductor and transformer loss factors to enable ‘virtual metering’ at high-voltage points from a low-voltage metering installation.

• Multiple communications ports that support simultaneous communications with numerous hosts and protocols. Rather than install various incompatible or high-burden devices on the CT and VT circuits, the designer can maximise the communications capabilities to incorporate layers to independently communicate with neighbouring meters, revenue data collection systems, SCADA, DCS, etc. In addition many new meters can be accessed by Internet and Intranet and accept connections via RF, copper-wire or fibre-optic cable, thus allowing the user to engage various communications service providers to facilitate data transfer.

• The remote terminal unit (RTU) master/slave capability to receive and hand-off metering and non-metering data to other entities is perhaps the most powerful of all. Depending on vendor software offerings, the client can now easily have a low cost SCADA-like dashboard on a local computer workstation in the general office and acquire analogue/digital data from other devices to assimilate and forward to other stakeholders.

The following brief case studies illustrate the various applications of the MEED in locations where only a revenue meter could be accommodated in the CT and VT circuits, but the client’s need for other data was also a requirement.

CASE 1 – LDC POLE METERING

Design Requirement:

• LDC presently metered inside another utility’s substation, has no asset ownership or control and receives scant realtime SCADA data from other devices in the substation.

• LDC wishes to have ISO-compliant MEED metering equipment installed on six of its own poles outside the substation perimeter, and will acquire pre-billing revenue information and expanded real-time SCADA data from its own equipment.

Existing LDC Assets:

• Owns the poles and conductors.
• Owns fibre-optic cable from pole metering equipment (PME) area to its headquarters.
• Available workstation in energy manager’s office for SCADA dashboard.
Smart Deployment:
• Selection of 12 suitably-equipped meters (MEED) for six PMEs; each PME has one main and one back-up meter.
• Each meter has simultaneous multiple-port communications
- Ethernet (10BaseT)
- RS-485
- RS-232
- Optical
• Utilisation of four different communications services/protocols
- Ethernet-over-fibre between six poles to one hub for LDC SCADA data
- Ethernet-over-fibre to LDC headquarters from hub
- RS-485 daisy chain over fibre to link 12 meters for ISO revenue data collection
- PSTN to one PME as a communications hub to RS-485 daisy chain.
Installed LDC Capabilities:
• ISO-compliant revenue metering with dial-up from ISO
settlements centre.
• Anticipate ISO billing and be in a position to dispute
discrepancies.
• Enhanced SCADA data such as:
- Per phase voltage and current;
- 4-quadrant watts and vars; and
- Power quality information such as total harmonic
distortion (THD) and sag/swells.
• Virtual breaker status without access to breaker pallets
- Use of meter’s voltage and current presence to interpret breaker position (breaker is open if all three phase voltages are zero)
- Meter logger provides sequence-of-events and internal meter diagnostics
• Depending on workstation setup, the energy manager can access SCADA data remotely from outside LDC headquarters.

CASE 2 – GENERATOR METERING AT INDEPENDENT POWER PRODUCER (IPP) FACILITY

Design Requirement:

• IPP wishes to have ISO-compliant MEED metering equipment installed on three dispatchable generators (>20 MW) at its new facility and will acquire pre-billing revenue information and expanded real-time system control and data acquisition (SCADA) data from its own equipment.
• MEED must include RTU capability to supply real-time data to ISO.
• MEED must include RTU capability to supply real-time data to transmitter.

Figure 1

Figure 1 – Case study 1, LDC Pole Metering

Figure 2

Figure 2 – Case 2, generator metering at Independent Power Producer (IPP) facility

Existing IPP Assets:
• Owns the gas insulated switchgear (GIS) substation (> 40 kV).
• Has ground potential rise-protected interface to public switch telephone network (PSTN) for ISO and grid transmitter communications circuits.
• Owns fibre-optic cable between substation and its headquarters.
• Available workstation in energy manager’s office for SCADA dashboard.
Smart Deployment:
• All meters located in a common lockable metering room in GIS building.
• Selection of 14 suitably-equipped meters (MEEDs) for six metering installations (MIs).
- Each MI has one main and one back-up meter
- Three MIs for gross generation
- Three MIs for net generation (allowing for parasitic load)
- Two meters act as RTU to ISO and transmitter respectively.
• Each meter has simultaneous multiple-port communications.
- Ethernet (10BaseT)
- RS-485
- RS-232
- Optical.
• Utilisation of six different communications services/protocols:
- Ethernet between six main meters to one hub for RTU data.
- Ethernet between six back-up meters to one hub for IPP SCADA data.
- External I/O interface to collect breaker status and analogue data from other intelligent end devices (IEDs).
- Ethernet-over-fibre to IPP headquarters from hub.
- Three RS-485 daisy chains to link 12 meters, in three groups of four, for ISO revenue data collection.
- PSTN to three RS-485 modems and their respective daisy chains.
Installed IPP Capabilities:
• ISO-compliant revenue metering with dial-up from ISO settlements centre.
• ISO-compliant real-time telemetry to ISO operations centre.
• Real-time telemetry to transmitter’s grid operations centre.
• Real-time telemetry to IPP operations centre for dispatch decisions.
• Depending on workstation setup, energy manager can access SCADA data remotely from outside IPP headquarters.
• Anticipate ISO billing and be in a position to dispute discrepancies.
• Enhanced SCADA data such as:
- Per phase voltage and current
- 4-quadrant watts and vars
- Power quality information such as frequency, THD and sag/swells.
• Breaker status from I/O access to breaker pallets
- Meter logger provides sequence-of-events and internal meter diagnostics.

CASE 3 – LARGE COMMERCIAL & INDUSTRIAL (LC&I) SITE METERING

Design Requirement:

• LC&I presently metered with non-MEED meters at two distant substations at one LC&I facility, and receives scant real-time SCADA data from legacy meters and other devices in the substations.
• LC&I wishes to have ISO-compliant MEED metering equipment installed on three of its own MIs at each substation, and will acquire pre-billing revenue information and expanded real-time SCADA data from its own equipment.
• LC&I wishes to integrate the SCADA from this facility with that of multiple facilities  for monitoring at corporate headquarters for dispatchable load options.
• LC&I requires DCS to receive separate data via RS-485.
Existing LC&I Assets:

• Owns fibre-optic cable between substations and its headquarters.

Figure 3

Figure 3 – Case 3, Large Commercial & Industrial (LC&I) site metering

• Available workstation in energy manager’s office for SCADA dashboard.
• Inter-facility communications to corporate headquarters.
Smart Deployment:
• Selection of nine suitably-equipped meters (MEEDs) for three MIs.
- Each MI has one main and one back-up meter, which both share the revenue CTs and VTs.
- Each MI has one check meter (on different CTs and VTs from revenue). Check meter will be used, with correction factors, by ISO in case main and back-up are both unavailable.
• Each meter has simultaneous multiple-port communications
- Ethernet (10BaseT)
- RS-485
- RS-232
- Optical.
• Utilisation of four different communications services/protocols:
- Ethernet between three main meters to one hub for LC&ISCADA data.
- Ethernet-over-fibre to LC&I headquarters from hub.
- RS-485 daisy chain over fibre to link nine meters for ISO revenue data collection.
- PSTN to one RS-485 modem and daisy chain.
Installed LC&I Capabilities:
• ISO-compliant revenue metering with dial-up from ISO settlements centre.
• Anticipate ISO billing and be in a position to dispute discrepancies.
• LC&I distributed control system (DCS) receives separate
data via RS-485.
• Enhanced SCADA data such as:
- Per phase voltage and current
- 4-quadrant watts and vars
- Power quality info such as THD and sag/swells
- Meter logger provides sequence-of-events and internal meter diagnostics.
• Depending on workstation setup, energy manager can access SCADA data remotely from outside LDC headquarters.

CONCLUSION

The robust capabilities of multifunction electronic end-devices together with creative applications and systems management by experienced solutions providers can enable today’s engineering or energy manager to better monitor and manage energy consumption and quality. These powerful and costeffective systems can provide energy reliability and management tools that can save costs and earn revenues for energy consumers, distributors, and producers in today’s dynamic energy environment.