Siemens 3VA21 Series

Siemens 3VA21 / 3VA22 — Mid-Range Molded Case Circuit Breakers with Electronic Protection

The Siemens 3VA21 and 3VA22 series extend the 3VA molded case circuit breaker family into the mid-to-upper current range from 630A to 1000A, featuring electronic trip units (ETU) as standard with optional metering, communication, and ground-fault protection functions. With over 2,200 variants, the 3VA21/3VA22 bridges the gap between compact MCCBs (3VA10/3VA11) and large-frame circuit breakers or air circuit breakers for main distribution applications.

3VA11 vs 3VA21/3VA22 — When to Step Up

The 3VA21/3VA22 is the correct choice when:

• Fault current exceeds 70kA at 400V (e.g., installations close to large distribution transformers)
• Selective coordination data is required for upstream-downstream breaker pairs — the electronic trip unit provides settable time-current curves for zone-selective interlocking (ZSI)
• Power monitoring is needed per circuit — the integrated metering function eliminates the cost and wiring of external current transformers and power meters at each feeder
• Communication to a building management system (BMS) or plant SCADA is required for remote status monitoring, event logging, and load management

ETU (Electronic Trip Unit) Features

The 3VA21/3VA22 electronic trip unit provides:

• LSI Protection: Adjustable Long-time (overload), Short-time (delayed short-circuit), and Instantaneous trip functions — the same protection functions as a thermal-magnetic breaker but with precise, repeatable, and settable thresholds.
• Ground-Fault Detection (ETU with GF function): Measures residual current via internal or external current transformer. Ideal for TT and TN-S earthing systems where ground-fault protection is a regulatory requirement (IEC 60364).
• Metering Function (ETU with M function): Measures voltage (via external voltage tap), current per phase, active/reactive/apparent power, energy (kWh), power factor, and frequency. Accuracy Class 1 per IEC 61557-12.
• Communication (ETU with COM module): Modbus RTU (RS-485), PROFIBUS DP, or PROFINET IO. Transmits breaker status (open/closed/tripped), trip cause (overload/short-circuit/ground-fault), and real-time metering values to the supervisory system.
• Event Logging: Stores the last 16 trip events with time stamp, trip cause, and current values at the moment of trip — invaluable for post-fault analysis without additional recording equipment.

Application Examples

• Main LV Switchboard Incomer: 3VA22 with 150kA breaking capacity protects the busbar system at the point where fault current is highest.
• Large Motor Feeder: 3VA21 with adjustable short-time delay coordinates with the downstream motor protection circuit breaker to ensure only the faulted branch is disconnected.
• Data Center Power Distribution: The integrated power metering per circuit feeds into DCIM (Data Center Infrastructure Management) software via Modbus TCP for energy efficiency tracking and capacity planning.
• Critical Process Industry: Zone-selective interlocking between 3VA21 breakers ensures a downstream fault is isolated by the nearest upstream breaker, preserving power to the rest of the plant.

Availability

3VA21/3VA22 circuit breakers are engineered-to-order items in many configurations. Standard 3-pole, ETU-only versions: 2-4 weeks from Siemens distribution centers. Units with metering function, communication modules, or 4-pole configurations: 6-10 weeks. Motor operators, rotary handles, and plug-in/withdrawable kits are ordered separately.