Expansion growth leads to users consuming more and more energy based on their demand. Energy transmission congestion results when energy transmission can no longer accommodate the increased power flow. Reasons for transmission congestion can vary, but the common demand issues for power flow on a specific route is not possible without risking its reliability. Lets identify common constraints and the consequences associated with them.
Transmission lines have their own thermal limit that can result in sagging lines if it is exceeded. This can result in a line fault, where electric arcing is experienced to the nearby vegetation, structures, and of course the ground. When this happens protective transmission components remove the faulty line in order to preserve terminal equipment from serious damage.
When the line is remove for repair other transmission lines experience increased loads to compensate for the loss. Overloading can result, which can lead to thermal limits exceeding its operational constraints. If this situation is not properly contained quickly the other lines compensating for the loss can experience the exact same scenario.
Understanding that this temporary fix is only for emergency situation and that energy transmission lines can still exceed its thermal limit. For this reason energy transmission lines often have an emergency rating. This rating gives a specific amount of time that allows higher load transfers in order for to minimize the chance of hitting the thermal limit.
Generally the energy transmission line reactance at the receiving ends is much less than the voltage applied at the starting end. Larger voltage deviations higher or lower than the nominal voltage value may cause equipment damage for the consumer or the provider. Which gives reason for having an operating voltage constraint to maintain operation that meet requirements. This constraint is much more important in areas where energy transmission lines are scatter and lengthy.
Loads constantly change, this can either be small or large changes. Relatively small changes in load generally occur when mechanical power on the generation side adjust to electrical demand. As long as the variation is small the connection between systems can remain in synch. The system would remain stable as long as the loads do not gain in magnitude and oscillate at low frequencies. These oscillations can lead to problematic voltages and frequency issues that can lead to instability and possibly outages.
Large oscillations occur due to servicing, faults, or disruption in energy transmission lines. Larger frequency ranges can cause uncontrollable situations that could result in non-steady-state instability. Preventative measures are necessary to minimize the potential instability.
Voltage instability happens when systems are exposed to larger reactive power flows. This is a result of the voltage difference from the starting to the receiving end of the line. This resulting in voltage drops at the receiving end. Lower voltages increase current and can contribute to losses. Voltage collapse is the end consequence. Potential causing equipment damage and possibly outages.
Defining Energy Transmission Line Design
There a number of considerations that factor into transmission line design. Energy transmission lines have specific parameters that define them. These parameters have implications on the environmental effects. The basic parameters include:
- Nominal Voltage
- Length of Line
- Altitude Range
- Design Loads
The nominal voltage is an approximation to what the actual line voltage would be. Actual voltage varies based on resistance, distance, connecting equipment, and the line’s electrical performance. Altitude range roughly means the expected weather and terrain encountered. Design load is also based on the weather factor. For example the design load that wind and ice put on the energy transmission lines and towers. This affects the tower dimensions, lengths, tower design, and conductor mechanical strength and wind dampening.
Tower Design Parameters
Transmission towers are designed to keep conductors separate from the local surroundings and each other. The higher the energy transmission voltages are the greater the separation distance needs to be. When an arc can jump from the transmission line to the ground causes a fault to ground scenario. This is when there is a transfer of electricity to the surroundings. This can also occur between the conductors. This is referred to a phase-to-phase fault.
The first design consideration is the distance between the conductors, the tower, and other potential arcing structures. This provides a general idea for the physical dimensions of the tower. This includes the tower height, conductor spacing, and insulator length for mounting.
Next design consideration is the structural strength of the tower frame to maintain the first design requirements. This takes into account the component, weather, and possible impact loads.
The final design consideration is to provide the necessary foundation to support the tower and the predetermined design loads.
Clearance Design Parameters
The basic function of the tower is to isolate conductors from the surrounding, other conductors, and potential arcing structures. Clearances based on phase-to-tower, phase-to-phase, and phase-to-ground. Phase-to-tower clearances are typically maintained by insulator strings that must take into account of possible conductor motion. The phase-to-ground clearance is based on the tower height, to minimize line temperature and the potential for line sag, and controlling vegetation and potential arcing structures. Phase-to-phase separation is controlled through tower geometry and limiting line motion.
Designing for Lightning Protection
The taller the tower the higher the chance for a potential lightning strike. Lightning strikes can cause considerable damage to energy transmission and consumer equipment. To minimize lightning strike damage an extra set of cables are run from the top of the tower to the ground for the lightning to follow. These are commonly referred to as shield wires and help ensure that equipment failure is prevented.
Designing for Conductor Motion Suppression
Weathering effects producing conductor motion can potentially cause damage to energy transmission equipment. The most common type of energy transmission damper is the Stockbridge damper. These are installed below the conductors, adjacent from the attachment point on the conductors to the tower. Adequate prediction for weathering effects can help in determining the damper design required for the transmission tower. These prevent the vibrational effects of weathering to potentially cause damage to utility equipment.
E3.Cable for Physical Design Layout
E3.Cable allows for a versatile blend of electrical and mechanical CAD combined into a sophisticated platform. This will provide tools and features that will make designing energy transmission lines, substation interconnections, and transmission towers easy and simple. Provides you with the needed features to keep designs from clashing while maintaining geometric requirements for mechanical structures.
Allows for the creation of interconnecting system panels and transmission lines with easy drag and drop snap in features. Create an easy error free design based on input parameters based on the user’s demand. Provides some of the following.
- Creates Physical Representation of Panel Controllers
- Design Rule Check
- Clash Detection
- Placement Error Prevention
E3.3D Routing Bridge
E3.3D routing bridge provides an easy transition between the most used MCAD softwares on the market to energy transmission line routing and configuration. Easily transfer MCAD files into the E3.3D routing bridge to determine energy transmission line length and diameter for design parameters. This provides an intermediate step between joining the mechanical and electrical engineering aspects in one easy to use software. E3.3D routing bridge provides a clearer image of interconnections between conductors, energy transmission lines, and insulators and the necessary clearance to achieve operational engineering parameters. It provides the follow features:
- Transferrable Component Information to MCAD
- Check for Component Clash in MCAD
- Accounting for Transmission Sag or Bends
- Calculate Length of Energy Transmission Lines and Segments in MCAD
The Right Design Tools
Understanding the design constraints and consideration is only the first step towards designing for the best energy transmission equipment. Having the best tools available to produce the best quality and reliability will serve engineers many magnitudes over. Take the next step in preparation design engineering.Comment on current design processes used for your transmission systems and how it could be better.