Current Transformers
Current transformers are critical electrical devices primarily used for current transformation and isolation. Current transformation occurs through magnetic flux coupling via the iron core. Current transformers not only enhance the measurement accuracy and protection reliability of electrical equipment but also simplify equipment design and manufacturing, thereby reducing costs.
The primary functions of current transformers include:
Transforming high currents into low currents at a fixed ratio for use by various instruments, relay protection systems, and automatic devices.
Zero-Sequence Current Transformers
Zero-sequence current transformers play a pivotal role as the "ground fault sentinels" in power systems and electrical protection. Their core function is to detect and measure zero-sequence currents in circuits, thereby identifying ground faults (such as leakage or single-phase grounding) and triggering protective devices to ensure personnel and equipment safety.
Zero-sequence current only appears when a circuit is in an abnormal operating state. Specifically, when a ground fault occurs in any one phase of a three-phase current, the earth voltage becomes zero while the high-voltage line maintains extremely high voltage.
Once the zero-sequence current reaches a preset threshold, the associated protection device will operate, tripping to cut off the power supply and prevent further damage.
1. Ground Fault Protection This is the core function. Zero-sequence current transformers detect ground faults by continuously monitoring the vector sum of phase currents. During normal operation, this vector sum equals zero. When a ground fault occurs, the vector sum deviates from zero. A zero-sequence current emerges, transmitting the induced zero-sequence current signal to a relay or trip device. When the current value exceeds the set threshold (e.g., 30mA, 100mA, 1A), the protection device rapidly cuts off the power supply, preventing electric shock casualties and electrical fires.
2. Detection and Monitoring
Used to monitor the insulation status and imbalance of power lines, enabling fault early warning. In large systems, it assists operators in locating the branch circuit of a ground fault.
3. Electrical Fire Prevention
The main residual current protection in building distribution boxes detects slow-developing or sudden leakage currents through zero-sequence current transformers. It promptly disconnects the faulty circuit, preventing fires at the source.
Enhancing Power Supply Reliability: In non-effectively grounded systems (e.g., low-resistance earthing systems), detecting the magnitude and direction of zero-sequence current enables "fault line selection." This accurately identifies the faulty circuit and issues an alarm without immediate tripping, allowing operators to address the issue systematically. This reduces both the scope and duration of power outages.
LVZW-35 current transformer
LVZW-35 current transformer is a sensor used to measure large current in 35kV system. It is mainly used in substations, power systems and electrical equipment. The transformer adopts magnetic core type, which is characterized by high linearity, strong anti-interference ability, small size and simple structure. It is a current transformer with very high cost performance.
1.Rated voltage：40.5kV
2.Primary current：50-1200A
3.Secondary current：5/1
4.Measurement level：0.2/0.2S/0.5/0.5S
5.Protection level：5P/10P
6.Installation method: vertical installation;
7.Applicable range: used with 35kV circuit breakers and transformers.
8.Product advantages：Safe and reliable, high measurement accuracy, wide measurement range, small size, light weight, good dynamic performance, low power consumption, convenient equipment standardization, easy to realize automatic monitoring and control.
Shaanxi West Power Tongzhong Electrical Co., Ltd. specialized in 7-40.5kV vacuum circuit breakeres for 20 years .
Our address
Nanpo Village, Chencang Avenue Jintai District Baoji City, Shaanxi Province, China.
86-18091765882
xdtz04@westpowerelectric.com
