In electric supply lines in India, which parameter is kept constant ?

In the Indian electric supply system, frequency is the parameter strictly maintained as a constant at 50 Hz [2]. While voltage is nominally 220V for domestic supply, it frequently fluctuates due to line losses, distance from transformers, and load variations [c2][t3]. Current and power are dynamic variables that change continuously based on the consumer's load demand [c4][t2]. Frequency stability is critical because it reflects the real-time balance between power generation and demand across the entire grid [t1][t4]. If supply exceeds demand, the frequency rises, and if demand exceeds supply, it falls; therefore, grid operators use Automatic Generation Control (AGC) to keep it at the standard 50 Hz to ensure the stability of synchronized equipment like motors and transformers [t4][t8]. Maintaining this constant frequency is essential for the synchronized operation of the national power grid [t1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > What you have learnt > p. 206
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > 12.4 DOMESTIC ELECTRIC CIRCUITS > p. 204