Network Solutions Guide for Smart Grids

SIEMENS – Network Solutions for Smart Grids

Introduction

A secure, reliable and economic power supply is closely linked to a fast, efficient and dependable communication infrastructure. Planning and implementation of communication networks require the same attention as the installation of the power supply systems themselves (fig.1).

Telecommunication for utilities has a long history in the transmission level of the power supply system and Siemens was one of the first suppliers of communication systems for power utilities. Since the early 1930s Siemens has delivered Power Line Carrier equipment for high-voltage systems. In today’s transmission systems, almost all substations are monitored and controlled online by Energy Management Systems (EMS).

The main transmission lines are usually equipped with fiber-optic cables, mostly integrated in the earth (ground) wires (OPGW: Optical Ground Wire) and the substations are accessible via broadband communication systems.

• The two proven and optimal communication technologies for application-specific needs are Synchronous Digital Hierarchy (SDH) and Ethernet.

Fiber-optic cables are used whenever it is cost-efficient. In the remote ends of the power transmission system, however, where the installation of fiber-optic cables or wireless solutions is not economical, substations are connected via digital high-voltage power line carrier systems.

Figure 1 – Complete communication network solutions to build a Smart Grid for power utilities

The situation in the distribution grid is quite different. Whereas subtransmission and primary substations are equipped with digital communication as well, the communication infrastructure at lower distribution levels is very weak.

In most countries, less than 10 % of transformer substations and ring-main units (RMU) are monitored and controlled from remote.

• The rapid increase in distributed energy resources today is impairing the power quality of the distribution network. That is why system operators need to be able to respond quickly in critical situations.

A prerequisite for this is the integration of the key ring-main units as well as the volatile decentralized wind and solar generation into the energy management system, and thus into the communication network of the power utilities.

Because the local environment differs widely, it is crucial that the right mix of the various communication technologies is deployed.

This mix will need to be exactly tailored to the utilities’ needs and the availability of the necessary infrastructure and resources (e.g., availability of fiber-optic cables, frequency spectrum for wireless technologies, or quality and length of the power cables for broadband power line carrier).

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Energy Management Guide

Energy Management Guide

Energy Management

Principles of Energy Management

Maintaining a reliable supply of electrical power to consumers is a highly complex process as most of this power cannot be stored and the individual components of this process, forming what is called a power system, can be spread over a wide geographical area.

• The purpose of power system management, also referred to as Energy Management, is to monitor, control and optimize this process in real-time.

The basic functionality of power system control is found in the Supervisory Control and Data Acquisition (SCADA) function that collects and records values and statuses acquired from the power system elements via remote telemetry to enable control center operators to supervise and control the power system.

Other decision support functions complement this function to provide power system management for a secure and optimal process (figure 1).

Figure 1 – Power control systems – serving the complete energy chain from generation to load

The Role of the Network Control System in Power System Management

History

The control and information technology used for the management of a power system has its origins in the automation of power plants. The primary objective was then to improve operational reliability (figure 2).

Figure 2 – Todays’ operator user interface of a large power control system

With the increasing number of power plants and their intercon- nection via the grid, primary frequency control, also referred to as generator droop control, was no longer sufficient. To improve on power delivery quality, coordination, including secondary frequency control, of power generation and, later, external interchange became unavoidable and was promptly implemented in control centers.

Before the introduction of the transistor in 1947, the vast majority of protection and control devices used in power system control were of electromechanical design.

In the early days, information was transmitted by means of relays and pulse techniques, but with the introduction of electronics it became possible to implement increasingly efficient transmission means. At the end of the 1960s, with the introduction of the first process control computer, the first computer assisted power and frequency control systems became possible.

As computers became more efficient in the 1970s, the switchgear in transmission networks was also gradually monitored and automated with the aid of power system control technology.

• In response to the growing demand for network control systems, a number of companies began developing standardized systems for these applications. The systems of that period can be called the first generation of network control systems.

Because of the inadequate graphics capability of computer terminals at that time, the master computers were used mainly for remote monitoring of unmanned stations or for performing calculations to support operations. The network state was displayed visually on large switch panels or mosaic walls that were also used to control the switchgear. Only as the performance of graphical displays improved were Operation management functions gradually transferred to VDU-based Workstations.

As computing power continued to increase in the mid-1970s, it also became possible to use computers for optimization processes.

• With the aid of optimization programs run initially as batch Jobs and later onlineas well, it was possible, for instance, to determine the most economical use of hydroelectric and thermal power plants.

These programs also provided a method of economically assessing the exchange of energy, a basic requirement for energy trading later on. Increasing computer power was, however, also harnessed to further develop man-machine communication towards greater user friendliness.

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Power Transformers Guide

Power Transformers Guide – SIEMENS

Distribution Transformers

Voltage Regulators

Siemens invented the voltage regulator in 1932 and pioneered its use in the United States. Voltage Regulators are tapped step autotransformers used to ensure that a desired level of voltage is maintained at all times. A voltage regulator comprises a tapped autotransformer and a tap changer.

The standard voltage regulator provides ± 10 % adjustment in thirty-two 0.625 % steps. Voltage Regulators with ± 15 % and ± 20 % regulation are available for some designs.

• Voltage regulators are liquid-immersed and can be 1-phase or 3-phase. They may be self-cooled or forced air-cooled. Available at 50 or 60 Hz and with 55 or 65 °C temperature rise, they can be used in any electrical system to improve voltage quality.

Voltage regulator ratings are based on the percent of regulation (i.e., 10 %).

For example, a set of three 1-phase 333 kVA regulators would be used with a 10 MVA transformer (e.g., 10 MVA 0.10/3 = 333 kVA). 1-phase voltage regulators are available in ratings ranging from 2.5 kV to 19.9 kV and from 38.1 kVA to 889 kVA (fig. 5.9-3).

Fig. 5.9-3: 1-phase voltage regulator, JFR

3-phase voltage regulators are available at 13.2 kV or 34.5 kV and from 500 kVA to 4,000 kVA.

Voltage regulators can be partially or completely untanked for inspection and maintenance without disconnecting any internal electrical or mechanical connections. After the unit is untanked, it is possible to operate the voltage regulator mechanism and test the control panel from an external voltage source without any reconnections between the control and the regulator.

Standard external accessories

The standard accessories are as follows:

• External metal-oxide varistor (MOV) bypass arrester
• Cover-mounted terminal block with a removable gasketed cover. It allows easy potential transformer reconnections for operation at different voltages
• Oil sampling valve
• Two laser-etched nameplates
• External oil sight gauge that indicates oil level at 25 °C ambient air temperature and oil color
• External position indicator that shows the tap changer position Mounting bosses for the addition of lightning arresters to the source (S), load (L) and source-load (SL) bushings. They shall be fully welded around their circumference.

Accessories and options

• Remote mounting kit: Extra-long control cable shall be provided for remote mounting of the control cabinet at the base of the pole.
• Sub-bases: To raise the voltage regulator to meet safe operating clearances from the ground to the lowest live part.
• Auxiliary PT: Operation at different voltages.

Testing

All voltage regulators shall be tested in accordance with the latest ANSI C57.15 standards.

Standard tests include:

• Resistance measurements of all windings
• Ratio tests on all tap locations
• Polarity test
• No-load loss at rated voltage and rated frequency Excitation current at rated voltage and rated frequency Impedance and load loss at rated current and rated frequency Applied potential
• Induced potential
• Insulation power factor test
• Impulse test
• Insulation resistance

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SIEMENS – Switchgears and Substations Guide

SIEMENS - Switchgears and Substations Guide (on photo: Sivacon S8 low voltage power)

Introduction

This guide covers three subchapters: High voltage substations, Medium voltage substations and Low voltage substations.

Low voltage main distribution

When selecting a low voltage main distribution system, the prerequisite for its efficient sizing is knowing about its use, availability and future options for extension. The requirements for power distribution are extremely diverse.

Normally, frequent switching operations need not be considered in the planning of power distribution for commercial, institutional and industrial building projects, and extensions are generally not to be expected. For these reasons, a performance-optimized technology with high component density can be used.

In these cases, Siemens mainly uses circuit-breaker protected equipment in fixed-mounted design.

• When planning a power distribution system for a production plant, however, system availability, extendibility, control and the visualization of status information and control functions are important issues related to keeping plant downtimes as short as possible.

The use of circuit-breaker protected technology in withdrawable design is important. Selectivity is also of great importance for reliable power supply. Between these two extremes there is a great design variety that should be optimally matched to customer requirements.

The prevention of personal injury and damage to equipment must however, be the first priority in any case. When selecting appropriate switchgear, it must be ensured that it is a design verified switchgear assembly (in compliance with AC 61439-2, VDE 0660-600-2), with extended testing of behavior in the event of an internal arc fault (IEC 61641, VDE 0660-500, Addendum 2).

Low voltage main distribution systems should be chosen among those featuring a total supply power up to 3 MVA.

Up to this rating, the equipment and distribution systems are relatively inexpensive due to the maximum short-circuit currents to be encountered.

For rated currents up to 32006, power distribution via busbars is usually sufficient if the arrangement of the incomingloutgoing feeder panels and coupler panels has been selected in a perfor-mance-related way. Ambient air temperatures, load on individual feeders and the maximum power loss per panel have a decisive impact on the devices to be integrated and the number of panels required, as well as their component density (number of devices per panel).

Low voltage switchgear example (SIVACON S8, busbar position at rear HxWxD: 2200x4800x600 mm)

Arc resistance

Arcing faults can be caused by incorrect dimensioning and reductions in insulation due to contamination etc., but they can also be a result of handling errors.

The effects, resulting from high pressure and extremely high temperatures, can have fatal consequences for the operator, the system and even the building. SIVACON offers effidence of personal safety through testing under arcing fault conditions with a special test in accor-dance with IEC 61641 (DIN VDE 0660-500 Addendum 21.

• Active protection measures such as the high-quality insulation of live parts (e.g. busbars), standardized and simple operation, prevent arcing faults and the associated personal injuries.

Passive protections increase personal and system safety many times over. These include:hinge and locking systems with arc resistance, the safe operation of withdrawable units or circuit breakers behind a closed door and patented swing check valves behind venitlation openings on the front, arcing fault barriers or arcing fault detection system combined with the rapid disconnection of arcing faults.

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Power Transmission and Distribution Solutions Guide – Siemens

The new Siemens’s high-voltage direct-current transmission (HVDC) system will secure the power supply in New Zealand

Solutions for Smart and Super Grids with HVDC and FACTS

The power grid of the future must be secure, cost-effective and environmentally compatible. The combination of these three tasks can be tackled with the help of ideas, intelligent solutions as well as advanced technologies.

• Innovative solutions with HVDC (High-Voltage Direct Current Transmission) andFACTS (Flexible AC Transmission Systems) have the potential to cope with the new challenges.

By means of power electronics, they provide features which are necessary to avoid technical problems in the power systems, they increase the transmission capacity and system stability very efficiently and help to prevent cascading disturbances.

The vision and enhancement strategy for the future electricity networks are, for example, depicted in the program for “Smart Grids“, which was developed within the European Technology Platform.

Features of a future smart grid such as this can be outlined as follows:

1. FLEXIBLE: fulfilling operator needs whilst responding to the changes and challenges ahead
2. ACCESSIBLE: granting connection access to all network users, particularly for RES and high -efficiency local generation with zero or low carbon emissions
3. RELIABLE: assuring and improving security and quality of supply
4. ECONOMIC: providing best value through innovation, efficient energy management and “level playing field” competition and regulation

Smart grids will help achieve a sustainable development. It is worthwhile mentioning that the smart grid vision is in the same way applicable to the system developments in other regions of the world.

An increasingly liberalized market will encourage trading opportunities to be identified and developed. Smart grids are a necessary response to the environmental, social and political demands placed on energy supply.

HVDC, FACTS and SIPLINK

Today’s power transmission systems have the task of transmitting power from point A to point B reliably, safely and efficiently. It is also necessary to transmit power in a manner that is not harmful to the environment. Siemens offers comprehensive solutions, technical expertise and worldwide experience to help customers meet these challenges.

For each application and technical transmission stage, Siemens offers optimized solutions with SIPLINK (Siemens Multifunctional Power Link), HVDC transmission or FACTS for the most efficient use of AC power systems and lines.

• Typical applications for FACTS include fast voltage control, increased transmission capacity over long lines, power flow control in meshed systems, and power oscillation damping.

With FACTS, more power can be transmitted within the power system. When technical or economical feasibility of conventional three-phase technology reaches its limit. HVDC will be the solution (fig. 1). Its main application areas are economical transmis-sion of bulk power over long distances and interconnection of asynchronous power grids.

Figure 1 - AC versus DC transmission cost over distance. The break-even distance amounts to 600km for a power transmission of 1000 MW.

Siemens’s latest innovation in high-voltage direct current technology is HVDC PLUS. The advantages of the new system, which employs voltage-sourced converters, include a compact layout of the converter stations and advanced control features such as independent active and reactive power control, and black start capability.

For medium-voltage DC transmission, Siemens offers the SIPLINK system. Depending on the application and the configuration of the existing system, SIPLINK will reduce investment, system and lifecycle costs.

The system controls the active power and opti-mizes voltage stability by providing reactive power.

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Basics of Switchboards – SIEMENS

Basics of Switchboards - SIEMENS (on photo: Sivacon S8 low-voltage power distribution board)

Switchboard Construction

Frame

There are multiple elements that make up a switchboard. Included in the list of elements are aframe, buses, overcurrent protective devices, service metering, and outer covers. The frame of the switchboard houses and supports the other components. The standard Siemens switchboard frame is 90 inches high and 32 or 38 inches wide.

An optional height of 70 inches with widths of 32, 38, or 46 inches is also available. Siemens switchboards have a depth measurement ranging from 20 to 58 inches.

Switchboard frame

Bus

A bus is a conductor or set of conductors that serves as a common connection for two or more circuits. NEC® article 408.3 states that bus bars shall be located so as to be free from physical damage and shall be held firmly in place.

Rear Connected Switchboards

Siemens Rear Connected (RCS) switchboards feature individually mounted branch and feeder devices. Because of this method of mounting, access to outgoing cable terminations must be from the rear of the switchboard.

Bus bar extensions from the feeder devices are run back to the rear of the unit for easy access. The front and rear of all sections align.

• Both indoor (NEMA 1) or outdoor (NEMA 3R) construction are available.

RCS switchboards accommodate systems up to 6000 amperes, 600 volts maximum in any three-phase three-wire or three-phase four-wire configuration. The main bus can be specified for 600 to 6000 ampere rating.

Rear Connected Switchboard

RCS Switchboards use WL insulated case (UL 489) or LV power (UL 1 066) circuit breakerswith drawout mountings and continuous current ratings from 400 to 5000 A for main and branch devices.

Integrated Power System  (IPS) Switchboards

The modular design of Siemens Integrated Power System (IPS) switchboard allows the customer to integrate electrical distribution equipment, power monitoring, and environmental controls that typically mount in multiple enclosures into one switchboard line-up.

Customers have the freedom to configure an arrangement that best fits their individual needs. Optional factory installed interconnection wiring is available to further reduce installation time.

IPS switchboards are built to UL 891 and NEMA PB-2 standards. IPS sections have a standard height of 90 inches. Optional 70 inch high sections are available. The minimum depth of IPS sections is 1 3.75 inches. Optional depths of 20, 28, and 38 inches are available and these optional depths may be required depending upon the components installed.

• Numerous components are available to fit customer requirements:
  • Lighting panelboards (MLO and main device)
  • Power monitoring devices
  • Distribution transformers
  • ACCESS communication
  • Lighting contactors
  • Lighting control
  • Heating ventilation and air condition (HVAC) control
  • Building management equipment
  • Programmable logic controller (PLC)
  • Automatic transfer switch (ATS)
  • Motor starters
  • Backup generators
  
  

IPS switchboards consist of one service section and one or more distribution sections that are cable connected. However, IPS switchboards are also available with through bus and pull sections.

IPS switchboards accommodate systems up to 4000 amps, 600 VAC maximum in 1 -phase, 3-wire; 3-phase, 3-wire; and 3-phase, 4 -wire configurations.

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Basics of Surge Protection

SIEMENS - Basics of Surge Protection

Causes of Surges

Surges can be caused by sources outside a home, such as when large electrical loads are turned on and off. Disturbances can result from the routine operation of electrical machinery at a nearby factory or large commercial facility, but they can also be caused by the electric utilities protective devices.

• The most damaging source of electrical surges, however, is lightning.

Lightning is caused by the attraction of positive and negative charges in the atmosphere. This results in a buildup and discharge of electrical energy.

Lightning can occur within a cloud, from cloud to cloud, or from cloud to earth. According to theNational Oceanic and Atmospheric Administration (NOAA), there are an estimated 2000 thunderstorms at any given moment in the world, resulting in 100 lightning strikes every second.

In the United States alone, there are over 22 million lightning strikes in an average year. A typical lightning strike might range from 20,000 to 1 00,000 amps at a potential of up to 30 million volts.

Electrical Equipment Damage

Lightning does not have to strike a home, or near a home to cause electrical damage. A lightning strike on a power line several miles away still has the potential to cause extensive electrical damage in a home.

• In addition to causing surges on the power line, lightning can also cause damaging surges on telephone lines and TV cables.

Thunderstorm Locations

Thunderstorms occur everywhere in the United States. The following map shows the approximate mean annual number of days with thunderstorms in the United States.

Surge Protection Terminology

There are a variety of SPDs available to protect sensitive electronic equipment from surges. In order to understand these devices, it is necessary to understand some basic terminology.

Joule Rating

One of the more common ratings for an SPD is the amount of electrical energy the device can absorb in a designated time without failing.

• This rating is sometimes called the joule rating because the joule (J) is a basic unit of measurement for energy. However, this rating is often referred to by other names such as transient energy rating or single pulse energy dissipation rating.

In theory, the higher the joule rating, the more energy an SPD can channel away from the protected circuit. However, procedures for testing the amount of single pulse energy that an SPD can dissipate without failing vary, so the joule rating should be considered in the context of other ratings provided by an SPD supplier.

One way to think about the concept of a joule of electrical energy is to relate it to another more familiar electrical unit, a watt. One watt is the basic unit of measurement for power, and power is the rate at which energy is used.

More specifically, for every watt of power, one joule of energy is used every second (joules = watts x seconds). This means that a common 7 5 watt light bulb uses 75 joules of energy per second.

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