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The dry-type current transformer is a critical component for precision current measurement and relay protection within modern power systems. Utilizing a solid insulation process—vacuum-cast epoxy resin or unsaturated resin—it operates completely free of oil, gas, and pollution. Designed based on advanced electromagnetic induction principles, it precisely steps down high primary currents to standard low secondary currents (5A or 1A). Highly compact and flame-retardant, it is widely installed in switchgears, distribution panels, and outdoor lines to ensure intelligent grid safety.
Core Parameters:
• Rated Voltage: 10kV / 20kV / 35kV.
• Accuracy Class: Measurement (0.2 / 0.5) | Protection (5P10 / 10P20).
• Structure: Solid Resin Cast (Class F/H Insulation, Maintenance-Free).
Product Features
Employs epoxy resin vacuum casting. It operates 100% oil-free, making it entirely leak-proof, non-polluting, highly flame-retardant, and self-extinguishing.
Available in strict measurement accuracy classes (0.2/0.5). Ensures flawless signal translation for precision energy metering and precise smart grid monitoring.
Dedicated protection cores (5P10/10P20) guarantee rapid and highly reliable responses to relay systems during severe electrical faults, preventing cascading grid failures.
Engineered with high rated short-time thermal current and dynamic stable current capabilities, enabling the unit to withstand intense electromagnetic shocks during short-circuits.
The dense resin-cast structure yields a tiny footprint and lightweight profile. It is incredibly easy to install inside compact medium-voltage switchgears and tight distribution panels.
Unlike oil-immersed or gas-filled transformers, the solid-state dry-type CT requires absolutely no fluid checks or gas pressure monitoring, saving significant O&M time.
Full Series Electrical Parameters (Current Transformer)
| Core Parameter | Standard Configuration Range | Application / Function |
| Rated Voltage | 10kV / 20kV / 35kV | Adapts flawlessly to standard medium and low-voltage distribution grid standards. |
| Rated Current Ratio | 50A~600A / 5A (or 1A) | The core ratio stepping down high primary line currents to safe secondary values. |
| Accuracy Class (Measurement) | Class 0.2 / Class 0.5 | Dictates the high precision required for revenue metering and standard instruments. |
| Accuracy Class (Protection) | Class 5P10 / Class 10P20 | Ensures reliable, un-saturated performance during massive fault currents for relay triggers. |
| Rated Short-Time Thermal Current | Customized per specific rated I_th | The maximum short-circuit current the unit can withstand thermally for a specified duration. |
| Rated Dynamic Stable Current | Customized per specific rated I_dyn | The peak electromagnetic force the CT can physically endure during a severe short-circuit. |
| Insulation Class | Class F (155℃) / Class H (180℃) | Solid resin casting ensures premium heat resistance, fire retardation, and moisture proofing. |
Detailed Description
The dry-type current transformer (CT) serves as the critical sensing node bridging high-voltage primary circuits with low-voltage secondary monitoring devices. Operating on fundamental electromagnetic induction laws, it securely steps down dangerous high currents into manageable 5A or 1A signals. Encapsulated entirely in vacuum-poured epoxy or unsaturated resin, it eradicates the limitations of traditional oil-immersed units, providing a compact, fire-resistant, and entirely maintenance-free operational life.
These versatile units feature dedicated secondary windings tailored for dual critical purposes: highly sensitive measurement cores (Class 0.2/0.5) for pinpoint energy metering, and robust protection cores (Class 5P10/10P20) designed to survive massive short-circuit currents and trigger protection relays instantaneously. Engineered to support 10kV to 35kV systems, they possess extraordinary thermal and dynamic stability, making them indispensable components for modern switchgear integration and smart grid automation.
FAQ
During normal operation, the secondary winding of a Current Transformer (CT) must always remain closed (short-circuited through low-impedance meters or relays). An open circuit on the secondary side is extremely dangerous for the following reasons:
1) Life-Threatening High Voltage: When the secondary circuit is opened, the opposing magnetic flux disappears. All of the primary current immediately acts as excitation current, causing the iron core's magnetic flux to spike to extreme saturation. This induces a lethal peak voltage on the secondary winding that can reach thousands of volts, endangering the lives of nearby operators.
2) Insulation Breakdown & Fire: The massive voltage spike will severely stress and likely puncture the resin insulation of the secondary windings and connected instruments, leading to permanent equipment destruction.
3) Severe Core Overheating: The saturated magnetic flux generates immense eddy currents and hysteresis losses in the iron core. This rapidly overheats the core, melting the resin casting and potentially starting a fire. If a measurement instrument needs to be removed, the secondary terminals of the CT must be securely short-circuited first using a dedicated test block.
Whatsapp: +86-13961294414
E-mail: junqiu.wang@czguanghui.cn
jocelyn.duan@czguanghui.cn
ADD: No. 1, Yulong Middle Road, Xuejia Town, Xinbei District, Changzhou City, China
Mobile: 0086-15380068868
