Definition: The maximum demand indicator is used to measure the maximum amount of power consumed by a consumer within a specific time interval. It is designed to measure base and peak loads, but it cannot measure sudden short - circuit currents or the high starting currents of motors. Its purpose is to record power consumption over specific periods.
The maximum demand indicators are categorized into four types:
- Recording demand indicator
- Average demand indicator
- Thermal type maximum demand indicator
- Digital Maximum Demand Indicator
Construction of Maximum Demand Indicator
The maximum demand indicator comprises five main components:
- A dial connected to the moving system
- A pointer
- A reset device
- A fraction device
- An indicating pin
The average demand indicator is integrated into the energy meter. Together, the energy meter and the average demand indicator measure the total power consumption and the maximum value of specific power within a particular time interval. The average demand indicator features a sophisticated speed - dial mechanism.
The pin drive advances the dial for a short period (e.g., half an hour). The total power consumed during that interval is displayed on the dial. The instrument has a cam that is regulated by timing gears. The cam resets the pointer to the zero position.
The pointer records the total power consumed by the load within that specific time interval. In the next half - hour, the pin moves forward again. However, the pointer will only move forward if the total power consumed by the load exceeds that of the previous period.
A formula is used to calculate the average maximum demand.
The maximum demand meter is capable of measuring power in terms of kilovolt - ampere - hours reactive (kVarh) or kilovolt - ampere - hours (kVah). This functionality is achieved by incorporating an appropriate meter that can compute these quantities accurately.
Advantages of Average Demand Indicator
- The average demand indicator offers a high degree of accuracy in measurement.
- It features a consistent and uniform measuring scale, ensuring reliable and comparable readings.
Disadvantages of Maximum Demand Indicator
- One of the primary drawbacks is the relatively high cost of the instrument, which can pose a significant investment barrier.
- Its construction is intricate and complex, requiring specialized knowledge and skills for installation, maintenance, and repair.
In modern applications, technological advancements have led to significant changes in its design. Specifically, the traditional cam mechanism has been replaced by an electromagnetic relay, and the bell crank releasing device is now commonly substituted with a clutch, enhancing operational efficiency and reliability.
