The general purposes earthing include:
§ Ensuring human safety.
.
By carefully evaluating these factors and referring
to earthing guidelines such those listed in
Table 4-1, MVDC system designers can select
the optimal earthing method balance safety,
reliability, and efficiency.
§ earthing system: The power line not
earthed, and only the conductive enclosure is
earthed.73 1.
Considerations for designing MVDC earthing
systems include:
§ Transient overvoltage: The earthing method
affects the amplitude and duration transient
voltages during faults.73
4.7
Dielectric strength cable 1.
§ Reducing equipment failures and minimizing
downtime.3 Earthing
Earthing and electrical protection are critical safety
considerations for any power system, including
MVDC operations.
§ earthing system: The conductive enclosure
of equipment not earthed independently but
is connected the neutral point the power
line through protective conductor.
§ Mitigating radiated and conductive
electromagnetic interference (EMI) and
minimizing electromagnetic compatibility
(EMC) issues.
§ Preventing electrical fires and arc accidents.5 2.
§ Fault current management: High-resistance
earthing effective enhancing safety,
reducing stress equipment and limiting fault
current magnitudes.
For low voltage, IEC 60364-1 classifies earthing
systems into three types based the earthing of
the power lines (system earthing) and the earthing
of the enclosures electrical equipment the
consumer side [44]:
§ earthing system: The power line (system
earthing) and the conductive enclosure of
equipment are independently earthed at
separate points.
§ System application: The choice earthing
depends the system’s operational priorities,
such cost, safety, EMI considerations, and
continuity power supply.
§ Corrosion risks: Earthing designs should
minimize long-term exposure metallic
electrodes leakage currents, especially in
TT systems, where corrosion risks are higher.37
MVDC technologies and operational considerations
Table 4-1 Selection guidelines for various earth systems [45]
Characteristic High impedance IT
Earth fault current High Low Low
Arc flash hazard High Very low Very low
Transient overvoltage 2. This directly influences
the insulation requirements cables and other
equipment
