What Is a Load Bank?

The load characteristic refers to the law that the active power and reactive power drawn by the power load from the power supply of the power system change with the voltage at the end of the load and the system frequency. The load characteristic is an important part of the power system. As a consumer of electrical energy, it has an important influence on the analysis, design and control of the power system.

The load characteristic refers to the law that the active power and reactive power drawn by the power load from the power supply of the power system change with the voltage at the end of the load and the system frequency.

Power load is an important part of the power system. As a consumer of electrical energy, it has an important influence on the analysis, design and control of the power system. A large number of load models have been proposed, including static load models, mechanical dynamic load models, and non-mechanical dynamic load models. At the same time, many measured parameters have also been accumulated. Establishing a load characteristic database can easily perform various queries and calls on historical data, and it is convenient to compare, analyze, synthesize and apply load characteristics from a whole and long-term range.

From the requirements of the load modeling system for the database, the load characteristic database must be safe, reliable, and easy to use. It is required to provide a large-capacity data warehouse that supports large-volume data transfers and quickly. In addition, in connection and operation with other databases The adaptation of the system should be more extensive. In view of this, the software and database are developed using Visual Basic 6.0 and SQL Server, respectively. Visual Basic is a visual, object-oriented, rapid application development tool, with powerful graphics and image processing functions, and powerful database functions. SQL Server has good ease of use, scalability, reliability and so on. This relational database management system can meet the needs of various types of enterprise customers and independent software vendors to build applications. In the establishment and application of load characteristics database of Jiangsu Power Grid and Henan Power Grid, it has been proved through practice that the load characteristic database can meet the engineering requirements ^[1]

The law that the load power changes with the voltage at the load point is called the voltage characteristic of the load; the law that the load power changes with the frequency of the power system is called the frequency characteristic of the load; the law that the load power changes with time is called the load's Time characteristics. But generally, the time characteristic of the load is called the load curve (the daily load curve, the annual load curve, etc.), and the voltage characteristic of the load and the frequency characteristic of the load are collectively called the load characteristic.

Reflects the relationship between load power and voltage (or frequency) after the change of the load point voltage (or power system frequency) reaches steady state, which is called the static characteristic of the load; reflects the load power during the sudden change of the load point voltage (or power system frequency). The relationship with voltage (or frequency) is called the dynamic characteristic of the load.

Load power is divided into active power and reactive power. The law of change of these two kinds of power is very different. By combining the above-mentioned various characteristics, a specific load characteristic is determined, such as the static frequency characteristic of active power and the static voltage characteristic of reactive power.

The main components of the load of the power system are asynchronous motors, synchronous motors, electric heating furnaces, rectifiers, lighting equipment, etc. At different load points, the proportion of these electrical equipment is different, and the power consumption is different, so the load characteristics are also different. ^[2]

The load characteristics have a great influence on the operating characteristics of the power system. For example, studying transients in power systems

In the analysis and calculation of power systems, there are generally four methods for simulating load characteristics.

Use a constant impedance (or constant power, constant current) to simulate the load. This is the roughest simulation method and is therefore only suitable for some approximate calculations. But because this method is relatively simple, it is widely used.

Use the static characteristics of the load to simulate the load. This method is more accurate than using a constant impedance (or constant power, constant current) to simulate the load. It is essentially a combination of three simple forms of constant impedance, constant current, and constant power in a certain proportion. This simulation method is generally used in dynamic stability and load flow calculations.

A load model considering the typical comprehensive load dynamic characteristics of the mechanical transient state of an induction motor. Because induction motors (see asynchronous motors) are the main components of power system loads, this load model is often used in transient stability calculations to consider the change in slip of an induction motor during transients versus the impedance of the steady-state equivalent circuit. Impact.

A load model considering the typical comprehensive load dynamic characteristics of the electromechanical transient process of an induction motor. This is a more accurate load model. It considers both the mechanical transient process of the induction motor and the electromagnetic transient process of the motor ^[3] .