Kode ANSI (ANSI Code)

Summary

The video introduces ANSI device and function numbers used in electrical protection diagrams. Understanding these codes helps readers identify the protective relays and functions installed in a generator or power system.

Reading a protection diagram

The presenter uses a single-line diagram of a power-generation system as an example. It appears to show a generator connected through a step-up transformer to a 230 kV system, along with another transformer that steps voltage down to around 4 kV for auxiliary or station-use equipment.

Current transformers (CTs) supply measurements to protection relays. They scale high system currents to values suitable for the relays.

ANSI device numbers identify protective functions. A code on a diagram indicates what kind of protection is provided and helps explain how the system responds to electrical faults or abnormal conditions.

Protection is layered. If a circuit breaker fails to open after receiving a trip command, backup protection can prompt an upstream breaker to operate. Diagrams should therefore be read with attention to both each protection function and its relationship to other equipment.

Protection functions also apply to specific zones. In the example, differential protection covers the generator area; other functions may protect different parts of the system.

ANSI functions discussed

• 50/27 — Unintentional energization: Protects against a generator being energized unintentionally.
• 50BF — Breaker-failure protection: Operates when a breaker fails to open after a trip command and can signal backup protection to trip an upstream breaker.
• 59 — Overvoltage: Protects against voltage exceeding an acceptable level. Depending on the design, voltage may be measured phase-to-phase or phase-to-neutral.
• 27 — Undervoltage: Protects equipment or a network when voltage falls too low.
• 24 — Overexcitation / volts-per-hertz (V/Hz): Protects against excessive magnetic flux associated with voltage and frequency conditions.
• 81O and 81U — Overfrequency and underfrequency: Protect against frequency rising above or falling below acceptable limits.
• 87 — Differential protection: Protects a defined zone, such as the generator, against internal faults.
• 21 — Distance protection: Also known as distance relay protection.
• 59GN — Generator-neutral overvoltage: The presenter associates this function with ground-fault protection on the generator side.

The example diagram also includes 40, 46, 60, and 32, which are not explained in detail. The presenter notes that some functions, such as codes 50 or 51, may appear on another panel or module.

Suggested approach to interpreting a protection diagram

1. Identify the equipment shown, such as generators, transformers, breakers, and CTs.
2. Locate the ANSI numbers beside relays or protection panels.
3. Look up unfamiliar numbers in a complete ANSI code list; simplified lists may omit less common combinations.
4. Connect each code to the equipment and protection zone it applies to.
5. Check how backup protection responds if a primary device—particularly a circuit breaker—fails to operate.

Speaker and sources

• Muhammad Azhari — presenter and identifiable speaker, associated with the Prima Aqute channel.
• Visual and reference material: A single-line electrical diagram and an ANSI code list, which the presenter says are available online and in the channel’s shared documents. No other speaking participants are identifiable in the subtitles.