What is Sag Template?

Edwiin
05/21/2025

Definition: A sag template is a tool used to accurately determine the positioning and height of supports on a profile. It defines the limits for vertical and wind loads, and also establishes minimum clearance angles between the sag and the ground for safety. Typically crafted from transparent materials such as celluloid or plexiglass (and occasionally cardboard), the sag template features the following marked curves:
  • Hot Template Curve (Hot Curve)
  • Ground Clearance Curve
  • Support Foot or Tower Curve
  • Cold Curve (Uplift Curve)
Detailed explanations of these curves are provided below.
Hot Curve: The hot curve is generated by plotting the sag values at the maximum temperature against the corresponding span lengths. It serves as a guide to determine the precise locations where supports must be positioned to ensure that the specified ground clearance requirements are met.
Ground Clearance Curve: Positioned below the hot curve, the ground clearance curve runs parallel to it. The vertical distance between these two curves is equivalent to the ground clearance value mandated by regulations for the particular line, thereby providing a clear margin for safety and compliance.
Support Foot Curve: This curve is specifically designed to aid in accurately locating the positions of supports for tower lines. It indicates the height measurement from the base of the standard support structure to the attachment point of the lower conductor. In the case of wood or concrete pole lines, however, there is no necessity to draw this curve, as these poles can be installed in any location that offers practical convenience.
Cold Curve or Uplift Curve: The uplift curve is derived by plotting the sag values at the minimum temperature under windless conditions against the span lengths. Its primary purpose is to assess the likelihood of conductor uplift on any support. Uplift of the conductor may occur at low temperatures, especially when one support is significantly lower than its adjacent supports, and this curve helps in identifying such potential scenarios.
Preparation of the Sag Template: Initially, the aforementioned curves are meticulously drawn on graph paper using the same scale as that of the line profile, with appropriate scales carefully selected for accuracy. Subsequently, with the assistance of a sharp - pointed probe, these curves are precisely transferred onto transparent celluloid or perspex sheets. Finally, the celluloid or perspex is cut along the line representing the maximum sag, which is the hot curve, completing the creation of the sag template.
Edwiin

How to Design and Install a Solar PV System?
How to Design and Install a Solar PV System?
Design and Installation of Solar PV SystemsModern society relies on energy for daily needs like industry, heating, transport, and agriculture, mostly met by non-renewable sources (coal, oil, gas). However, these cause environmental harm, are unevenly distributed, and face price volatility due to limited reserves—driving demand for renewable energy.Solar energy, abundant and capable of meeting global needs, stands out. Standalone PV systems (Fig 1) offer energy independence from utilities.
Edwiin
07/17/2025
Load Frequency Control (LFC) & Turbine Governor Control (TGC) in Power System
Load Frequency Control (LFC) & Turbine Governor Control (TGC) in Power System
Brief Introduction to Thermal Generating UnitsElectricity generation relies on both renewable and non - renewable energy resources. Thermal generating units represent a conventional approach to power production. In these units, fuels such as coal, nuclear energy, natural gas, biofuel, and biogas are combusted within a boiler.The boiler of a generating unit is an extremely complex system. In its simplest conception, it can be visualized as a chamber whose walls are lined with pipes, through which
Edwiin
06/06/2025
Why 3-Phase Power? Why Not 6, 12 or More for Power Transmission?
Why 3-Phase Power? Why Not 6, 12 or More for Power Transmission?
It is well-known that single-phase and three-phase systems are the most prevalent configurations for power transmission, distribution, and end-use applications. While both serve as fundamental power supply frameworks, three-phase systems offer distinct advantages over their single-phase counterparts.Notably, multi-phase systems (such as 6-phase, 12-phase, etc.) find specific applications in power electronics—particularly in rectifier circuits and variable frequency drives (VFDs)—wher
Edwiin
06/05/2025
How Many Poles and Towers are Situated Within a 1-km Span?
How Many Poles and Towers are Situated Within a 1-km Span?
The number of distribution poles and transmission towers within a 1-kilometer stretch of overhead lines varies significantly based on multiple factors, including voltage level, power line type, supporting structure, geographical location, local regulations, and specific grid requirements.In urban areas, distribution utility poles are typically positioned at closer intervals, while in rural regions, they are spaced farther apart. Additionally, the use of taller structures for higher-voltage trans
Edwiin
06/05/2025
Inquiry
Download
IEE-Business is dedicated to serving the personnel in the global power industry.
Join IEE-Business, not only can you discover power equipment and power knowledge, but also canhnd like - minded friends!