A Guide to Power Analysis and Measurement

• 2023-07-29

The optimum working condition of any process/equipment can only be achieved through observing and analyzing all the parameters that affect efficiency. One of these is power - every piece of process/equipment requires power to run and thus power consumption and power quality measurements ultimately become a part of the process/equipment design and test.

But how do you measure this? What methods and instruments can be used? How do these instruments operate? This article shall discuss and answer all these questions.

What is power?

Starting from the fundamentals, electrical power is essentially how fast an electrical equipment or machine uses energy. It is defined as the rate at which electrical energy is transferred through an electrical circuit. The SI unit is watt (W). Other common units are kilowatts (kW), megawatts (MW) and milliwatts (mW). It is important to note the difference between power and energy. They cannot be used interchangeably. Power is the capacity to consume electrical energy while energy represents the flow accumulated over time.

Why do we need power analysis?

First, lets understand why its necessary to measure power. As world-renowned management consultant Peter Drucker said, If you cant measure it, you cant manage it.

Keeping track of all the parameters that can have an effect on your equipment is critical, more so with high accuracy. Electrical power must be utilized to the highest efficiency possible to ensure the proper functioning and long life of the equipment. This enables the operation to be smooth, efficient and safe. This also reduces loss in the equipment, resulting in an increased life expectancy.

Having information on power needs allows us to improve the performance of pieces of equipment and services in the future, make sure the parameters are in compliance with government standards and eventually reduce cost and time consumption. It also reduces environmental pollution.

Power analyzers are designed to do just that. They make it easy for the user to monitor all the complex processes with only a few operations.

How is power measured?

Power measurements differ depending on the type of supply - true power (also called real power or active power) for DC circuits and apparent power, active power and reactive power for AC systems. This is done by calculating power consumption per complete cycle.

What are Wattmeter?

Wattmeter is a device that measures the active power of a circuit upon receiving a voltage input and current drawn. It generally consists of a current coil and a potential coil. The working principle of wattmeter is based on electromagnetic induction.

Using devices like a wattmeter, the multiplication of instantaneous current and instantaneous voltage can be calculated which is then integrated over one cycle time period. This provides us with true power measurements for any waveform.

Inputs of Wattmeter's

Wattmeter's have four terminals. Two terminals for voltage input and two terminals for current input (which come from CT output or, if the current is 5A or less, directly from line wires).

Types of power analyzer

Depending on what system they would be most suitable for, wattmeter's can be classified as:

• Single-phase power meter (two-wire system)
• two-phase power meter (three-wire system)
• three-phase power meter (four-wire system)
• three-phase power meter (three-wire system)

Three-phase, three-wire system

In two wattmeter power measurement method, voltage across two phases and respective currents are given to two wattmeter's, keeping any one phase common.

Three-phase four-wire system

In this system (R, Y, B phase and Neutral), the voltage across each phase and neutral is measured and algebraic multiplication is done with respective phase current. Total system power is obtained as a summation of the three-phase readings.

Multispan Power Meters

Picking the right power meter is extremely crucial to safeguarding your expensive equipment. You want a device that can pre-emptively warn you about overcurrent or overvoltage power factor of each phase and if possible voltage and current harmonics levels scenarios. If not done correctly, it may lead to electrical fires and permanent damage to your equipment. Multispan promises such acute precision with its power meters.

Multispan offers a range of power meters to perfectly suit various complex systems. With a long life, minimal maintenance required and a clear interface, these devices are very user-friendly and easy to operate. They come in several sizes, with an elegant ultra-bright LED display and universal auxiliary supply. Site programmable CT and PT ratio available.

Frequently Asked Questions

What is power system analysis?

A power system analysis examines and studies multiple aspects of a network system, be it generation, relaying or supply of electricity. There are conducted to make sure the networks are safe, reliable and in perfect working condition.

What are some power measurement devices?

Examples of power measurement devices include voltmeter, ammeter, wattmeter's, power analyzers, power meters, and power transducers.

What are some different ways of measuring electrical power?

The method for measuring electrical power is chosen depending on the type of input current supply. If a DC supply is received, voltage and current are directly measured by voltmeters and ammeters and used to calculate power (P=V*I). If the input is single-phase AC, the effective power is measured using wattmeter's. With a three-phase AC supply, the total effective power is measured using three-phase wattmeter's.

What is the purpose of fault analysis in power?

Fault analysis serves the critical purpose of detecting any issues that might lead to failures and potential damage. If the prescribed range of voltage or current is exceeded, it can result in fatal consequences. Fault analysis is needed to understand what actions need to be carried out to ensure system stability.