By Ginni Stieva, Power Measurement
April 2, 2004 — When power producers look to connect to the electrical grid, they must meet the information needs of all involved parties: generator owners, transmission companies or ISOs, and facility operators.
Often these needs are quite different: generator owners typically want precise cost/profit accounting for their generation units; while transmission companies and ISOs need timely information on compensated output measurements and energy used by the generator facility for market settlement and billing. On the receiving end, facility operators need enough data to manage operations, verify billing, and satisfy investors and partners.
Addressing these challenges requires the right kind of power-monitoring solution. Power producers can save as much as $250,000 per metering point by carefully monitoring factors such as combined instrument/transformer loss compensation, aggregation and scaling of real-time data, power factor, and integration of MV90 applications.
EEM offers a solution
An enterprise energy management (EEM) system can help. An EEM system typically consists of a network of intelligent revenue meters reporting to a centrally located computer workstation running the “head-end” software. Some of the meters monitor the feeds between generators and transformers to track the output from online generators. Others monitor the station loads, so that when the generators are offline, the facility operator can track and verify charges for the energy drawn from the grid to power the facility.
This type of configuration offers several advantages. The EEM system supervises generation assets in real-time, and allows for automated or manual control of functions. Plus, a choice of communication links enable meters to continuously send data to the head end software via telephone, microwave, wireless, Ethernet, and Internet networks, using industry standard protocols such as DNP 3.0, Modbus and MV-90.
Direct Ethernet links between intelligent devices and software ensure that data is transferred at maximum speeds, and web-enabled meters allow access to power system data via a standard web browser.
Accurate and affordable compensated measurements
Market settlement data must be made available to utility billing and operations departments, to the transmission company, and possibly to external owners of the generators. That means tracking the generation facility’s output to the grid, while taking into account transformer loss. However, monitoring this type of output at the logical point, after the power has passed through the transformer (on the primary high voltage side), can be extremely expensive.
Intelligent meters used on the secondary-side are up to $250,000 less expensive per high-voltage metering point than the alternatives. This is due to advanced metering technology available today that uses a series of algorithms to accurately account for transformer and instrument losses from the secondary side of the transformer.
Data collection can be complicated by the fact that the generators within a facility may be owned by different outside interests. In those cases, each generator must be monitored individually so that costs and profits can be accurately allocated to the owners of the different generators.
For plants that use three-winding GSU transformers, which can connect to more than one generator, advanced meters can track the output, uptime and downtime of each generator and accurately assign energy costs and gains to the appropriate generator owner, based on contract agreements.
Aggregation, scaling and submission of real-time data
To ensure the accurate accounting for the power supplied to and credited by the transmission company, near real-time market settlement data must be consistently made available to the necessary audiences through a resilient channel. Lost data means lost revenues, so maintaining a strong communication channel and reliable backup data is critical.
One option is using Modbus Master-enabled meters to obtain real-time information from all sub-meters (Modbus slaves) connected to their Modbus loop. These can perform scaling and aggregation, then write scaled values to a central data collection point.
Not only does this Modbus system simplify the data-collection process, it also provides a valuable backup function. Because the advanced power meters can store logged data as well as sending it to the central data collection point, if the data transmission to the central database is disabled in any way, a complete record of generation activities is still available by directly accessing the logged data stored in the meters.
Alternative communication channels also allow both the power producer and the transmission company to connect directly to individual meters when necessary to verify data, and can include serial, wireless, modem and Ethernet connections.
Because utilities often use MV90 as the backbone of their billing systems, advanced meters need to communicate directly with the MV90 software.
The information can be sent to MV90 at user-defined intervals (in minutes, hours or days), so that it is available whenever necessary for billing functions.
Other possibilities include power factor. For utilities whose contractual agreements with the generator owners include power factor standards, advanced revenue meters can track both lagging and leading power factor continuously – a necessary capability because power factor readings can vary during different periods when power is delivered or received.
In these times of shrinking budgets and competitive pressures, utilities need to continuously monitor generation assets across the entire enterprise. Monitoring energy enterprise wide can help reduce costs, while meeting the information needs of all parties, from the generator owner to the facility operator.
For more information, visit http://www.pwrm.com or call 250-652-7100.