MeGaElectrical

To the engineers interested in OHTL design, you can find below two supportive & helpful toolkits. The first one is associated with the calculation of the OHTL sag_tension_clearance_lenghts-graphs at any weather condition and also under any tower configuration and there are some features enhanced in the tool that is not available in the PLS-CADD lite like the calculation of the actual length of the conductor, the tool enables you to save a clearance above any object beside the towers span wherever it is, also it is not dependant on the available power line libraries of the conductor as you can deal with any conductor however its construction, and enable you to calculate the tension at supports in case of oblique wind case. However, before using it you should run the macro module on your PC. Noting that the toolkit is designed based on the parabolic analysis, the strain-stress phenomenon is applied only in the linear region, the vertical tension at the supports is ignored and the horizontal tension is the only considered, and the creep in the conductor is ignored. the design is based on: CIGRE 324 - Touran gonen_Electrical power transmission engineering_Analysis and Design - Overhead Power Lines- planning, design, construction - nolasco, et al -IEC TR 61597 The second one is associated with the calculation of the OHTL AC resistance, ampacity, inductance, and capacitance at any weather condition and also under any tower configuration based on the 1 ft method regarding the inductance & capacitance. the design is based on: - IEC TR 61597 - IEEE 738 - Aluminum Electrical Conductor Handbook_Larry #electrical #design #OHTL #CIGRE #IEEE #IEC

#How_is_the_current_carrying_capacity_of_the_cables_to_be_calculated? IEC 60287-1 & IEC 60287-2 provides a guide to the calculation based on transferring the heat dissipation model into an equivalent electrical circuit as per the installation conditions and the cable construction. One of these circuits as shown in Figure 1 represents the equivalent electrical circuit of cable installed in a shaded place and not exposed to the sun, and another one in Figure 2 represents the equivalent circuit of the cable directly exposed to the sun which in both of them: -The thermal resistances of cable-layers (T) transferred into electrical resistances -Heat losses in the cables or heat gained by radiation from the sun (W) transferred into current sources -Temperature at any surface separating between two adjacent layers (0) transferred into electric voltage where, -Wc=1^2 x R represents the heat losses in the conductor. -Wd=2 x πx f x C x Uo ^2 x tan(6) represents the dielectric losses in the insulation. -Ws = x1 x Wc represents the circulating and eddy losses in the metallic screen. -Wa = x2 x Wc represents the circulating, eddy losses, and hysteresis losses in the metallic armor. -Wsun = o x D x H represents the heat gained by radiation from the sun. -n represents the number of conductors in the cable. Then, from the electrical equivalent circuit, we can calculate the current for cable not exposed to the sun, as: A0 = (Wc+ 1/2 Wd) T1 + [Wc + Wd + Ws] n T2 + [Wc + Wd + Ws + Wa] n (T3 + T4) For cable exposed to sun, as: A0 = (Wc+ 1/2 Wd) T1 + [Wc + Wd + Ws] n T2 + [Wc + Wd + Ws + Wa] n T3+ [Wc + Wd + Ws + Wa + Wsun] n T4 IEC 60287 provides a simple guide also for the calculation of the losses in the metallic screen (11) and armor (12) and the thermal resistivity (T) of the different cable layers and surrounding mediums based on the cable construction and installation method. For further information regarding the cables, you can join my course at the below link. Follow #MeGa_Electrical

#Why_shall_we_bond (#connect) #the_cable_metallic_screen_to_the_ground? 1-To maintain a continuous safe fault current return path either through the metallic screen or a ground continuity conductor because if not, the fault current will pass through the ground levels/surface or any surrounding metals like pipes or train rails which have a huge resistance which in return will induce a lot of voltages on these surfaces and also on the source earthing system according to (V=I*R) and that will be very dangerous to the humans and animals. 2- To assure that the induced voltages on its metallic screen caused due to the transformer coupling with the conductor will not be high in normal operation or during faults, especially at its ends which this voltage could shock any person dealing with the cable 3-Also as we know this induced voltage is directly proportional to the current passing in the conductor so in the case of some over-voltage transients existing in the cable will cause a high transient current to pass in the conductor, then a very high voltage will be induced on the metallic screen and because the outer sheath it is not an insulating material and can withstand only limited voltage as shown in Figure 3, this will result in punching the outer sheath and when that occurs the moisture will ingress through the cable layers leading to a treeing in the insulation and that will cause high electric stresses on the cable insulation, then a complete breakdown may occur. For more illustration with a practical case, you can show in Figure 1 below transient over-voltage occurs in 345 KV cables causing an induced voltage of about 160 KV as in Figure 2 which is higher than the insulating capability of the outer sheath as in Figure 3. Thus, how is the cable screen bonded to the ground? The easiest way ever is to bond the cable on both ends by the grounding system but we will face big trouble only in the case of single-core cables due to the current caused by the induced voltage will circulate in the metallic screen because of the availability of a closed path, and that current will cause a heat loses in the cable and in return will decrease the current carrying capacity of the cable. So, For most of the distribution medium voltage cables and some of the transmission high voltage cables with a current carrying capacity that does not exceed 500 A, the circulating current losses are low and in this case only, both end bonding is appropriate. On the other hand, if the current carrying capacity. if the current carrying capacity exceeds 500 A a special bonding scheme eliminating this circulating current shall exist by letting one end of the metallic screen not be connected to the ground and the selection of the appropriate bonding scheme shall be based on the value of the induced voltage resulted on this end. For further information regarding the cables, you can join my course at the below link. #follow_MeGa_Electrical #The_cables_optimum_design_course

#Power_system_Overview

Transducers Types of Transducers

#Electrical_Safety

#Substation_Components: Substations are essential in power systems, serving as nodes where voltage levels are adjusted, electrical power is distributed, and various electrical protections are implemented. Here are the main components found in a #substation: #Power_Transformers: Step up or step down voltage levels to facilitate efficient power transmission and distribution. #Circuit_Breakers: Automatically interrupt power flow during faults, preventing damage to equipment and ensuring safety. #Isolators (#Disconnectors): Used to isolate portions of the circuit for maintenance by providing a visible break in the connection. They operate only when the line is de-energized. #Lightning_Arresters: Protect substation equipment from voltage surges due to lightning or switching events by diverting excess voltage to the ground. #Current_Transformers (#CTs): Measure high current levels by stepping them down to a manageable level for metering and protection relays. #Potential_Transformers (#PTs): Step down high voltage to a lower level suitable for measurement and protection. #Busbars: Conductors that serve as a common connection point for multiple circuits, allowing distribution of power to different lines. #Protection_Relays: Monitor parameters like current, voltage, and frequency to detect abnormalities and signal circuit breakers to trip in case of faults. #Capacitor_Banks: Provide reactive power compensation to maintain voltage stability and improve power factor. #Wave_Traps: Used in carrier communication within substations, they trap high-frequency signals and separate them from the power frequency. #Earthing (#Grounding) #Systems: Protect personnel and equipment by dissipating fault currents safely into the earth. #Control_Panels: Allow operators to monitor and control the substation components, with displays for realtime data and alarme. #Battery_Banks_and_DC_Systems: Supply DC power to control circuits and protection devices to ensure continued operation even if AC power fails. Each component in a substation plays a critical role in ensuring efficient and safe power transmission and distribution.

#TRANSFORMER_INRUSH_CURRENT: Transformer inrush current is the high surge of current that flows into a transformer when it is initially energized. This occurs because the transformer's magnetic core can become saturated due to the initial voltage applied. When the core saturates, it requires more current to establish the magnetic flux, leading to a large inrush current that can be up to 5-10 times the rated current of the transformer. This surge typically lasts only a few cycles (milliseconds) but can cause issues such as mechanical stress, insulation degradation, and unwanted tripping of protection systems. #Key_factors_influencing_transformer_inrush_current_include: #Magnetic_Core_Saturation: When the core reaches saturation, it needs a higher magnetizing current. #Residual_Magnetism: If there's any remaining magnetism in the core from the last operation, it can increase inrush current. #Switching_Point_on_Voltage_Wavefor: Energizing a transformer at or near the voltage waveform's peak increases inrush current. #Transformer_Design: Core material and design influence the inrush current magnitude. Inrush current is commonly managed using inrush-limiting devices, controlled switching techniques, or differential protection settings.

#PROTECTIVE_RELAYS: Protective relays are critical devices used in electrical power systems to detect faults and abnormalities, and to initiate the isolation of faulty components to protect equipment and ensure system stability. Here's an overview: #Types_of_Protective_Relays: #Electromechanical_Relays: Traditional relays that operate on the principles of electromagnetic induction. They are reliable but have a slower response time. #Solid-#State_Relays: Use semiconductor components, offering faster operation and improved accuracy. #Digital_Relays: Microprocessor-based relays with enhanced functionality, flexibility, and self-monitoring capabilities. #Numerical_Relays: Advanced relays that provide digital communication, remote control, and additional diagnostics. #Key_Functions_of_Protective_Relays: Fault Detection: Detects issues like overcurrent, overvoltage, underfrequency, or grounding faults. #Isolation: Triggers circuit breakers or switches to isolate the faulted section. #Monitoring_and_Communication: Modern relays can provide real-time monitoring and communicate with control systems for better fault analysis. #Common_Types_of_Relay_Protection_Schemes #Overcurrent_Protection: Activates during excessive current flow, often used for protecting lines and feeders. #Distance_Protection: Detects and isolates faults based on the distance from the relay to the fault point, commonly used in transmission lines. #Differential_Protection: Compares current between two points to identify internal faults in transformers, generators, and motors. #Directional_Protection: Determines the direction of fault current, helpful in systems with multiple power sources. #Under/#Overvoltage_and_Frequency_Protection: Ensures safe operation of equipment by monitoring voltage and frequency. #Advantages_of_Protective_Relays: #Safety: Reduces risk of damage to equipment and personnel by quickly detecting faults. #Reliability: Enhances system stability and prevents cascading failures. #Cost-#Efficiency: Minimizes costly downtime and equipment replacement. #Smart_Features: Digital and numerical relays offer advanced diagnostics and connectivity for remote operation. Protective relays play a crucial role in maintaining the integrity of electrical power systems, especially in industries, utility networks, and high-power applications.

#BUSBAR_PROTECTION: Busbar protection is a critical aspect of power system protection focused on safeguarding busbars in substations. Busbars are crucial nodes where multiple circuits (incoming and outgoing) converge, making them essential for the distribution of electrical power. Protection of busbars ensures the reliability and stability of the power system and minimizes damage and service interruptions in the event of faults. Here are some common methods of busbar protection: #Differential_Protection: Differential protection is widely used for busbars. It operates based on the principle that the current entering a busbar should equal the current leaving it. If there's a difference, it indicates a fault within the busbar zone. Typically, current transformers (CTs) are installed at each connection to the busbar, and any imbalance between incoming and outgoing currents triggers a trip signal. #Overcurrent_Protection: Though not as fast or selective as differential protection, overcurrent protection can be used as a backup for busbar faults. It detects an abnormal current rise due to faults, but it cannot distinguish if the fault is specifically in the busbar zone without selectivity. #Frame-#Earth (#or_Frame_Leakage) #Protection: This method is based on detecting fault currents flowing between the busbar frame and ground. A CT is connected between the frame and earth, and any abnormal current indicates a fault, potentially in the busbar or nearby equipment. #Low-#Impedance_Differential_Protection: Low-impedance differential protection uses low impedance relays to detect faults in a specific busbar zone. It is fast and highly reliable, as it responds quickly to large differences in current, making it suitable for high-speed protection of critical busbars. #High-#Impedance_Differential_Protection: High-impedance differential protection is a simple and cost-effective method suitable for busbars. It uses high impedance to limit the fault current and operate only when a significant fault occurs within the protected zone. #Directional_Protection: This method utilizes directional relays to sense the direction of fault currents and isolate the affected section. Though less common in busbars, it may be applied when there's a need for fault directionality information. Each method has specific applications depending on the complexity, importance, and configuration of the busbar in the power system.