| Gapped Silicon-Carbide Arrester | Silicon-carbide non-linear resistor blocks connected in series with internal spark gaps. | Legacy medium-voltage and older substation installations where replacement compatibility is required. | Commonly 5 kA or 10 kA, depending on the design and applicable standard. | Selected by system maximum voltage, grounding method, and the arrester's rated voltage. The gap must withstand normal system voltage without continuous conduction. | Generally lower and less consistent than modern gapless metal-oxide designs because the spark-gap voltage contribution varies with current and front-of-wave steepness. | Performance depends strongly on gap design, discharge history, and power-frequency follow current. Temporary overvoltage capability must be checked from the specific test curve. | Suitable for like-for-like maintenance in legacy systems; no continuous leakage current through the resistor blocks during normal operation. | Larger physical size, possible follow current, aging of gaps, and less predictable fast-front protective performance. | Use primarily for retrofit compatibility. For new installations, compare against gapless metal-oxide technology. |
| Gapless Metal-Oxide Distribution Arrester | Zinc-oxide metal-oxide varistor blocks without series spark gaps, normally enclosed in polymer or porcelain housing. | Distribution transformers, overhead distribution lines, switchgear, motors, generators, and medium-voltage equipment. | Frequently 5 kA or 10 kA for distribution applications; higher values may be specified for severe exposure. | The continuous operating voltage, Uc or MCOV, must be suitable for the highest continuous phase-to-ground voltage. Rated voltage, Ur, is normally higher than Uc and must also accommodate temporary overvoltage. | Good clamping performance and fast response. Residual voltage is normally specified at defined 8/20 microsecond current values rather than as one universal number. | Good energy absorption for ordinary distribution duties, but the arrester must be coordinated with fault current, line discharge class, and expected lightning exposure. | Compact, fast responding, no power-frequency follow current, and widely available in medium-voltage configurations. | Excessive continuous voltage, repeated temporary overvoltage, moisture ingress, or inadequate thermal protection can cause premature failure. | Confirm Uc/MCOV first, then compare residual voltage, energy capability, housing insulation, and disconnector behavior. |
| Gapless Metal-Oxide Station-Class Arrester | High-energy zinc-oxide blocks with a mechanically robust housing and carefully controlled thermal and pressure-relief design. | High-voltage substations, transformer terminals, busbars, cable terminations, generator step-up transformers, and critical transmission equipment. | Commonly 10 kA or 20 kA for station and transmission duties; the specified class depends on the system and exposure. | Uc/MCOV is selected from the maximum continuous phase-to-ground voltage. Ur must be coordinated with temporary overvoltage duration, grounding conditions, and insulation coordination studies. | Very good protective performance when selected with a low residual-voltage ratio and installed with short, low-inductance connections. Protection level must remain below the equipment insulation withstand level with a suitable margin. | High energy capability and improved thermal stability compared with basic distribution designs. Switching-surge energy may govern the selection on transmission systems. | High reliability, strong energy handling, low protection levels, and suitability for expensive power-system assets. | Higher cost and greater sensitivity to incorrect voltage selection. It may be unnecessarily large for ordinary low-exposure distribution points. | Select by insulation-coordination study, switching and lightning energy, short-circuit requirements, and equipment criticality. |
| Line-Discharge-Class Arrester | Gapless metal-oxide arrester categorized by its ability to withstand line-discharge energy associated with long overhead lines and cable systems. | Transmission-line entrances, cable-to-overhead transitions, long cable circuits, and substations exposed to significant switching energy. | Often 10 kA or 20 kA, with the required line-discharge class determined by system voltage and network configuration. | Uc/MCOV must satisfy continuous voltage and temporary overvoltage conditions; Ur alone is not sufficient for final selection. | Strong performance against both lightning impulses and switching surges when the line-discharge class and residual-voltage characteristics are correctly matched. | Designed for repeated or high-energy discharge duty. Energy rating should be verified using the applicable line-discharge test class and system study. | Appropriate for high-energy transmission environments and long-line switching events. | May be oversized for short, lightly exposed circuits. Incorrect installation distance can still produce excessive voltage at the protected equipment. | Use when line length, cable capacitance, switching operations, or network studies indicate substantial discharge energy. |
| Polymer-Housed Arrester | Metal-oxide arrester blocks enclosed in a silicone-rubber or other polymeric weather housing, usually with a pressure-relief and disconnector system. | Outdoor distribution and substation installations, polluted environments, compact switchgear, and locations requiring low weight and high contamination performance. | Commonly 5 kA, 10 kA, or 20 kA, depending on the internal arrester design and application class. | Uc/MCOV, Ur, phase-to-ground voltage, temporary overvoltage, and external insulation level must all be checked. Housing creepage distance must suit the pollution severity. | Electrical protection is determined by the internal metal-oxide blocks; polymer housing improves outdoor insulation behavior and reduces the risk of dangerous fragmentation. | Energy capability varies by internal design and is not determined by the housing material alone. Verify thermal stability, pressure relief, and energy-test data. | Lightweight, hydrophobic surface, good pollution performance, reduced breakage hazard, and easier handling. | Housing aging, seal degradation, ultraviolet exposure, and mechanical damage must be considered in harsh environments. | Prefer for many outdoor applications after confirming creepage distance, mechanical loads, sealing, and arrester energy class. |
| Porcelain-Housed Arrester | Metal-oxide arrester blocks enclosed in glazed porcelain with conventional external insulation and pressure-relief arrangements. | Outdoor substations and installations where established mechanical and insulation practices favor porcelain housings. | Commonly 10 kA or 20 kA for station and transmission applications; lower ratings are also used in distribution systems. | Select Uc/MCOV and Ur according to system voltage, grounding, temporary overvoltage, and insulation coordination requirements. | Can provide the same electrical protection level as an equivalent metal-oxide design when the internal blocks and test ratings are comparable. | Energy capability is determined by the arrester block design, thermal stability, and pressure-relief performance, not by porcelain alone. | Long-established technology, high mechanical strength, and predictable external insulation dimensions. | Heavier and more brittle than polymer housing; broken porcelain can create hazardous fragments during severe failure. | Consider where existing substation standards, mechanical loads, or lifecycle practices specifically favor porcelain. |
| Low-Voltage Type 1+2 Surge Protective Device | Low-voltage surge protective device combining high-current impulse capability with protection against induced and switching surges, typically using spark-gap and/or metal-oxide technology. | Main distribution boards, service entrances with an external lightning protection system or high lightning exposure, and industrial low-voltage installations. | Impulse current Iimp is commonly specified for Type 1 duty; nominal discharge current In is commonly specified for Type 2 duty. Values must be selected for the installation risk and system arrangement. | Select the maximum continuous operating voltage, Uc, above the applicable system voltage and verify the voltage protection level, Up, is below the withstand level of connected equipment. | Good coordinated protection when installed at the service entrance with short conductors and correctly selected backup overcurrent protection. | Must withstand the expected lightning current share, prospective short-circuit current, and temporary overvoltage specified by the low-voltage installation design. | Protects complete low-voltage systems and can coordinate with downstream Type 2 and Type 3 devices. | Incorrect lead length, poor bonding, wrong system configuration, or inadequate backup protection can severely reduce effectiveness. | Verify system earthing arrangement, Uc, Iimp/In, Up, short-circuit rating, backup protection, and coordination with downstream SPDs. |
