What Is Power Monitoring?
Power Monitoring is the process of measuring and monitoring the amount of electricity or power used.
Electricity is an energy that cannot be visually monitored for usage, but must be purchased from the power company if you do not have a power generation facility. Therefore, in order to ensure that the electricity bill is reasonable, it must be monitored using a watt-hour meter or a power monitoring system.
Traditionally, the purpose of power monitoring has been to reduce the cost of electricity. In recent years, it is not only for that purpose, but also as part of environmental protection activities such as CO2 reduction.
Electricity is an energy source that tends to account for a large proportion of business activities. Therefore, power monitoring is one of the most important items in energy management.
Uses of Power Monitoring
Power Monitoring is an activity that is widely implemented in commercial and industrial settings. It may also be implemented in homes.
The following are some examples of power monitoring:
- Power monitoring in large facilities
- Electricity generation monitoring in commercial facilities with solar panels
- Daily power monitoring for households
Companies and organizations with large facilities often install power monitoring systems. These systems often allow the user to see not only the power consumption of the entire facility, but also the usage by facility and sector. Detailed analysis of energy consumption status is possible, allowing for efficient energy conservation studies and power management.
Facilities with solar panels or generators may also provide power monitoring of power generation. In recent years, power usage at home can also be managed through the development of applications by electric power companies.
Principle of Power Monitoring
Power Monitoring is done mainly by measuring current, voltage, and power factor. Electricity is obtained by multiplying current and voltage. However, as the current and voltage shift out of phase, no power is effectively consumed.
Power can be calculated not only by multiplying the RMS values of current and voltage, but also by the power factor, which is the ratio of phase matching.
Current transformers (CTs) are commonly used to measure current, and voltage transformers (VTs) are commonly used to measure voltage; the current and voltage measured by CTs and VTs are calculated by wattmeters and converted to electric power while calculating the power factor. In the case of watt-hour meters, the power measured by these devices is integrated over time and output as electric energy.
The power generated by out-of-phase currents and voltages is called reactive power. When reactive power is generated, current that is not consumed by the load travels back and forth across the transmission line, putting pressure on the transmission facility capacity, which is disadvantageous to the power company. Therefore, when concluding a power contract for high-voltage or higher, a discount item for maintaining a high power factor is often included.
Structure of Power Monitoring
Electricity contracts for residential use are generally ampere contracts. Although the upper limit of the current is fixed by the ampere contract, if more load devices are connected, the current will exceed the contracted amount. However, under an ampere contract, if the number of load devices increases, the breaker will shut off the power supply when the current exceeds the contracted current.
On the other hand, facilities that receive power under high-voltage or special high-voltage contracts are uneconomical because of the time and effort required to restore power if power is interrupted. In public facilities such as hospitals, human lives may be at stake. Therefore, electric power companies often conclude power contracts on a demand charge basis, rather than shutting off power when the maximum limit is exceeded.
The demand charge system is a system in which the contracted power is based on the upper limit of the expected 30-minute average power; both the customer and the power company monitor the 30-minute average power value, and if the contracted power is about to be exceeded, the customer responds by limiting the power used. If the contracted power is exceeded, the power company will charge a penalty or review the contracted power.
Management of the 30-minute power forecast under the demand charge system is called demand monitoring. For consumers with high-voltage or higher, power monitoring is performed by installing a power monitoring system capable of monitoring the 30-minute average expected power consumption value on a minute-by-minute basis and limiting the power consumption.