HVDC Crowbar System for Arc Fault Protection

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Solution Overview

Problem

High voltage DC systems face challenges in rapidly responding to fault conditions such as feeder short circuits and arc faults, leading to potential damage and safety issues due to existing protection methods being inadequate at higher voltage levels.

Innovation Solution

A high voltage DC system incorporating a crowbar system with a switch module that can short AC lines together to prevent current flow to the rectifier in case of overcurrent, overvoltage, or arc faults, utilizing sense modules to detect thresholds and activate the switch module for fast protection, and a generator control unit to manage the generator output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional protection methods are used in high voltage DC systems, then the system can operate with existing equipment, but the response time to fault conditions is insufficient leading to potential damage

Engineering Contradiction:

Improveprotection response effectivenessVSAvoidfault response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The crowbar system is pre-configured with switch modules connected across the generator terminals, ready to immediately short-circuit the generator in case of fault conditions. This preliminary positioning of protection elements enables instantaneous response without waiting for fault detection and signal processing, directly resolving the time delay issue in conventional protection methods

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention bypasses the conventional sequential protection process by using sense modules that directly trigger switch modules through voltage thresholds. When a fault condition is detected, the system rushes through the protection action immediately by allowing the pre-charged capacitor banks to discharge through the crowbar resistors, eliminating delays associated with complex control logic and signal processing

Inventive Principle:

Principle #21Skipping (Rushing through)

2Reliability

If contactors are used to isolate fault conditions, then the system can be protected, but the contactors become significantly degraded after performing the isolation function

Engineering Contradiction:

Improvefault isolation capabilityVSAvoidcontactor service life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The crowbar system uses resistors designed to be replaced rather than repaired, and the switch modules are positioned to handle the full fault current without mechanical wear. This approach accepts that the crowbar components will be consumed or degraded but protects the more valuable contactors and generator, extending the overall system life by sacrificing less critical components

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The crowbar system acts as an intermediary protection device between the generator and the contactors. By placing the crowbar resistors and switch modules in parallel with the generator terminals, the system provides an alternative path for fault current that prevents direct stress on the contactors, thereby extending their operational life while maintaining effective fault isolation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If higher system voltage levels are used to increase power capability, then more power can be transmitted, but overcurrent and arc fault conditions become more dangerous

Engineering Contradiction:

Improvesystem power capabilityVSAvoidarc fault damage potential

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The crowbar system incorporates resistors specifically sized to limit fault current at the higher system voltage levels. By pre-calculating the appropriate resistance values based on the increased voltage, the system cushions the impact of potential arc faults and overcurrent conditions before they can cause damage, enabling safe operation at higher power levels

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables rapid protection against overcurrent, overvoltage, and arc faults, minimizing damage to equipment and ensuring safety by quickly isolating the fault, thereby extending the life of contactors and supporting safety requirements.

Implementation Method 1

The switch module can be configured to short each AC line together to cause phase summation to cancel the current to the rectifier

Methodology Applied

Scientific EffectPhase summation cancellation:

Data Source

PatentEP4178055A1High voltage DC systems

Publication Date: 2023.05.10 HAMILTON SUNDSTRAND CORP

Figure 1
Figure 2

AI summary

A high voltage DC (HVDC) system can include a generator (101) configured to output alternating current (AC), a rectifier (103) connected to the generator (101) via AC phase lines, the rectifier (103) configured to convert the AC to DC to output the DC to DC feeder lines, and a crowbar system (109). The crowbar system (109) can include a switch module operatively connected to the AC phase lines to prevent AC from flowing to the rectifier (103) in a cutoff state. The crowbar system (109) can be configured to determine whether at least one cutoff condition exists. The at least one cutoff condition can be or include one or more of a DC overcurrent downstream of the rectifier (103), a DC overvoltage downstream of the rectifier (103), an AC overcurrent from the generator (101), or an arc fault. The crowbar system (109) can be configured to control the switch module to the cutoff state if the at least one cutoff condition exists.