Moreover, pin type insulators are extensively used in substation equipment such as circuit breakers, https://pin-up-site.in/en-in/ isolators, and busbars, ensuring the safe and reliable operation of these critical components. Beyond this level, their performance declines, and they are not as effective in handling higher voltages. For high voltage systems, suspension insulators or polymer pin insulators are more suitable. For high-voltage transmission lines, stronger pin type insulators are used.

• It can be assumed that Brookfield may have had poor quality control as their insulators seem to be found with the most imperfections, however, this could be disputed.
• The flashover is caused due to the arc discharge between the conductor and the earth through air surrounding the insulator.
• Pin type insulators offer several advantages that make them a preferred choice in electrical transmission systems.
• The petticoats or rain sheds are so designed, that even when the outer surface is wet due to rain, sufficient leakage resistance is still provided by the inner dry surfaces.
• Their simple construction and easy installation make them a budget-friendly option for utility companies and residential power networks.

Why are pin insulators not used for higher voltages?

The distance between earth & conductor, insulator surrounding, and electrical discharge through the air is called flashover distance. It includes two main parts namely porcelain as well as galvanized steel bolt. There are a variety of techniques for protecting insulator toward the bolts. Pin insulators, particularly those made from polymer or composite materials, require minimal maintenance. Their self-cleaning ability due to rain and wind helps keep the insulator surface clean, minimizing the need for manual cleaning and reducing long-term operational costs. The insulators are bell-mounted to prevent water being held in contact with the spindle.

Ensuring proper installation and periodic inspection is crucial for the long-term performance of pin insulators. Excessive mechanical load, especially in multi-piece insulators, can lead to damage or failure. This is particularly problematic in high voltage systems where the insulator must bear more weight. Pollution, moisture, and weather conditions can accelerate the degradation of pin insulators.

• For these the ratio of the spark-over voltage to the working voltage (usually known as safety factor) must be high for low voltage than for high voltage.
• These insulators are available in different parts like 1 part, 2 parts or 3 parts type based on the voltage of application.
• This type was amongst the earliest designs, and used for support­ing line conductors.
• Pin insulators are primarily used for voltages up to 33 kV, and for higher voltages, composite pin insulators or polymer pin type insulators are preferred due to their superior weather resistance and UV resistance.

As the voltage increases, the use of multiple pieces in pin insulators adds weight, which increases the mechanical stress on the insulator mounting pin. This can lead to damage in extreme weather conditions or during heavy mechanical loads. Composite pin insulators and polymer pin insulators are becoming more popular due to their durability and recyclability. These materials offer a more sustainable option, with improved weather resistance insulator properties, allowing them to perform well in extreme conditions. The pin insulator is used in power distribution for the voltage up to 33kV. The pin insulator has grooves on the upper end for keeping the conductor.

Such an arrangement combines the ad­vantages of both of the above two types of insulators and overcome their disadvantages. Surface leakage current is due to the accumulation of dirt and in order to reduce its value the insulators are given a long leakage path by providing two or three petticoats or sheds. Insulators of this type are used on intermediate poles on straight run. The insulator has to endure from the potential stresses which occur between the earth & conductor.

It requires high safety factor value so that a flash-over occurs once before the pin type insulator gets punctured. For this kind of insulator, the safety factor value is approximately 10. The puncture of an insulator can be occurred due to the electrical discharge from the conductor to pin throughout the insulator. Enough thickness of insulator material must be used to evade a puncture. When such type of puncture occurs then the insulator will be damaged permanently. The designing of an insulator must be done properly to overcome the electrical and mechanical stresses on the insulator.

Another major U.S. manufacturer that produced glass insulators was the Hemingray Glass Company. Different colors were produced to allow two or more different utility companies to quickly identify which wires were theirs by the color of insulator if multiple wires were strung over the same utility pole. For example, one company may have a string of amber insulators, while another, on the same poles, might have their insulators in cobalt blue. Once the insulator gets wet, then its external surface will become almost conducting. The conductor is connected on top of the insulator and the base of the insulator can be connected for supporting earth potential structure.

Certainly, the transmission lines are always supported by insulators which are placed on the poles. The insulators which are used on the towers must have these properties like high mechanical strength, high electrical resistance, high relative permittivity, etc. The material of the insulator used in the transmission lines is porcelain but based on the requirement, steatite or glass type is also used. There are different kinds of insulators available in transmission lines like pin type insulator, suspension, strain, stay and shackle. The insulators like pin, strain, and shackle are applicable in medium to high voltage systems whereas shackle and stay are applicable in low voltage applications. Pin type insulators are widely used in electrical systems to secure electrical conductors to overhead lines.

The insulator body consists of multiple insulating units, or sheds, strategically designed to enhance the insulator’s electrical performance. These sheds are arranged in a circular or petticoat pattern, maximizing surface distance and minimizing the risk of electrical discharge or arcing. Additionally, the insulator is equipped with a base, often made of cement or resin, to provide mechanical stability and facilitate installation on the supporting structure. The wet flash-over and dry flash-over voltages for shackle insulators are 10 kV and 25 kV respectively while the puncture voltage is about 35 kV. Its operating voltage is 1,000 V. Its weight, transverse mechanical load and total creepage distance are 0.5 kg, 1,150 kg and 63 mm respectively. The tapered hole in the shackle insu­lator distributes the load more evenly and reduces the possibility of breakage when heavily loaded.

These insulators are available in different parts like 1 part, 2 parts or 3 parts type based on the voltage of application. One part type is used in an 11 kV power distribution system where the entire insulator is a porcelain/glass shaped piece. In wet conditions, pin type insulators can be susceptible to puncture failure due to the creation of a conductive path when moisture accumulates.

However, a number of porcelain and glass insulators are still in use, for example, the Dhalkebar-Muzaffarpur (India) 400 kV line or the Khimti-Dhalkebar 220 kV line. Shackle insulators may either be mounted horizontally or vertically, and the conductors are fixed in the grooves by means of soft copper or aluminium binding wire according to the conductor material. They can be directly fixed to the pole with a bolt or to the cross-arm. In such a construction, each insulator disc is symmetrically placed and it conforms to the electrostatic lines of force, thus avoiding placing materials of different permittivity’s in series. The metal work consists of pressed steel spiders, the legs of which are fastened into the porcelain by an alloy having approxi­mately the same coefficient of cubical expansion as the porcelain.

They are compatible with electrical distribution systems, offering flexibility in installation and use. These insulators provide reliable electrical flashover prevention and are designed to withstand mechanical stresses. The combination of mechanical strength and electrical resistance ensures continuous and stable performance in power systems. The sufficient thickness of the material is provided in the insulator to prevent the puncture under surge condition. The flashover is reduced by increasing the resistance to leakage currents. The length of the leakage path is made large by constructing several layers called petticoats or rain sheds.

3 Vulnerability to Puncture

The high-voltage pin type insulators differ in construction from low-voltage type in that they consist of two or three pieces of porcelain cemented together. Beyond this, suspension insulators or polymer pin insulators are preferred. Pin type insulators are a reliable and cost-effective solution for low to medium voltage power systems. With their durable performance, low maintenance, and versatility, they remain an excellent choice for many electrical transmission applications.

They offer a cost-effective solution for low to medium voltage transmission systems, ensuring the safety of electrical distribution systems and preventing accidents due to electrical faults. While composite pin insulators and polymer pin insulators provide certain advantages over traditional materials, pin insulators are still a popular choice due to their reliability and ease of use. Pin insulators are primarily used for voltages up to 33 kV, and for higher voltages, composite pin insulators or polymer pin type insulators are preferred due to their superior weather resistance and UV resistance. Substation insulators and insulator mounting pins are also commonly used in power stations and substations to maintain safe electrical isolation between conductive parts.

They are the earliest developed overhead insulator compared to shackle insulator, but are still commonly used in power networks up to 33 kV system. Pin type insulator can be one part, two parts or three parts type, depending upon application voltage. In a 11 kV system we generally use one part type insulator where whole pin insulator is one piece of properly shaped porcelain or glass. (vi) In case of rapid increase in load on transmission line, the increased demand can be met by raising the line voltage than to provide another set of conductors.

The suspension insulator hangs from the cross- arm of the supporting structure and the line conductor is attached to its lower end. Because there is no pin problem, we can put any distance between the cross-arm and the conductor just by adding more insulators to the “string”. Regular inspections for wear, cleaning to prevent pollution buildup, and ensuring proper mechanical load distribution are crucial for maintaining pin insulators. Under high-voltage conditions, pin insulators may experience flashover, particularly when the creepage distance is insufficient. This is more likely to occur when the insulator is subjected to environmental factors like pollution or moisture.

Their resistance to electrical tracking and erosion ensures long-term reliability and performance. When the pin type insulator is installed on a tower or pole, the electrical current flows through the conductor (the metallic pin) and reaches the insulator body. The insulating material resists the flow of current, ensuring that it cannot pass through to the supporting structure. Instead, the current is diverted along the pin and safely grounded, preventing any damage or electrical hazards. Pin type insulators possess several key components that enable them to perform their function effectively.

Electrical stress on insulators mainly depends on the line voltage, and therefore, appropriate insulators have to utilized based on the line voltage. Surplus electrical pressure can damage the insulator either by puncture or flash-over. While pin insulators are advantageous, they come with limitations that should be considered in specific applications. The pin insulator uses non-conducting material like porcelain, ceramic, silicon rubber, polymer, etc., The weight of the polymer pin insulator material is more as compared to porcelain insulator material. Flashover voltage, which refers to the voltage at which an electrical discharge occurs across the insulator surface, is influenced by factors such as surface condition. The flashover voltage for moist and dirty surfaces is generally lower than that for clean and dry surfaces.

Pin type insulators are a critical component of electrical transmission systems, ensuring the safe and efficient transmission of electricity. Designed to withstand high voltages, these insulators provide insulation between overhead power lines and supporting structures. With the increase in operating volt­age, the insulation required increases.