{"id":48237,"date":"2026-02-02T21:04:29","date_gmt":"2026-02-02T21:04:29","guid":{"rendered":"https:\/\/maritimehub.co.uk\/?p=48237"},"modified":"2026-02-02T21:04:29","modified_gmt":"2026-02-02T21:04:29","slug":"power-management-systems-pms","status":"publish","type":"post","link":"https:\/\/maritimehub.co.uk\/power-management-systems-pms\/","title":{"rendered":"Power Management Systems (PMS)"},"content":{"rendered":"\n<p>Load Sharing \u2014 When Generators Fight Each Other<br><br>Introduction \u2014 load sharing is where \u201chealthy\u201d systems quietly kill ships<\/p>\n\n\n\n<p>Many vessels lose power <strong>without any generator actually failing<\/strong>. Engines run, fuel is clean, cooling is normal \u2014 yet the ship blacks out.<\/p>\n\n\n\n<p>The cause is often <strong>poor load sharing<\/strong>.<\/p>\n\n\n\n<p>When generators are paralleled, they must agree on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>how much real power (kW)<\/strong> each carries<\/li>\n\n\n\n<li><strong>how much reactive power (kVAr)<\/strong> each supplies<\/li>\n\n\n\n<li><strong>how fast<\/strong> they respond to load changes<\/li>\n<\/ul>\n\n\n\n<p>If they don\u2019t, the PMS becomes a <strong>conflict amplifier<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">What load sharing actually means onboard<\/h2>\n\n\n\n<p>Load sharing is split into two distinct control problems:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1\ufe0f\u20e3 Real power sharing (kW)<\/h3>\n\n\n\n<p>Controlled by:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>engine governors<\/li>\n\n\n\n<li>droop or isochronous modes<\/li>\n\n\n\n<li>PMS supervisory logic<\/li>\n<\/ul>\n\n\n\n<p>Poor kW sharing causes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>one generator overload<\/li>\n\n\n\n<li>another underloaded<\/li>\n\n\n\n<li>trips that look \u201crandom\u201d<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2\ufe0f\u20e3 Reactive power sharing (kVAr)<\/h3>\n\n\n\n<p>Controlled by:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>AVR droop settings<\/li>\n\n\n\n<li>excitation limits<\/li>\n\n\n\n<li>voltage setpoints<\/li>\n<\/ul>\n\n\n\n<p>Poor kVAr sharing causes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>voltage instability<\/li>\n\n\n\n<li>excitation saturation<\/li>\n\n\n\n<li>generator protection trips<\/li>\n\n\n\n<li>cascading collapse<\/li>\n<\/ul>\n\n\n\n<p>ETO trap:<br>Crews monitor kW carefully and <strong>ignore kVAr until it\u2019s too late<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Droop vs isochronous \u2014 not just theory<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Droop control<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>allows stable parallel operation<\/li>\n\n\n\n<li>generators share load proportionally<\/li>\n\n\n\n<li>frequency varies slightly with load<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Isochronous control<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>holds frequency constant<\/li>\n\n\n\n<li>requires one \u201cmaster\u201d unit<\/li>\n\n\n\n<li>unstable if misconfigured<\/li>\n<\/ul>\n\n\n\n<p>Incorrect combinations (e.g. two isochronous governors online) cause:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>hunting<\/li>\n\n\n\n<li>load oscillation<\/li>\n\n\n\n<li>breaker trips<\/li>\n\n\n\n<li>blackout<\/li>\n<\/ul>\n\n\n\n<p>This is not a tuning issue \u2014 it is a <strong>system design violation<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udd27 Regulatory anchors (explicit)<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">IEC 60092-201<\/h3>\n\n\n\n<p>Requires:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>stable power supply under normal operation<\/li>\n\n\n\n<li>suitable arrangements for parallel generators<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">SOLAS Chapter II-1, Regulation 42<\/h3>\n\n\n\n<p>Requires:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>sufficient power for propulsion and essential services<\/li>\n\n\n\n<li>ability to operate systems simultaneously<\/li>\n<\/ul>\n\n\n\n<p>If load sharing causes a generator trip under normal load, the ship is <strong>not compliant in practice<\/strong>, even if compliant on paper.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udd3b Real-World Case: MV <em>Viking Sky<\/em> \u2014 Load Instability Before Generator Loss (2019)<\/h2>\n\n\n\n<figure class=\"wp-block-image aligncenter is-resized\"><img decoding=\"async\" src=\"https:\/\/www.lloydslist.com\/-\/media\/lloyds-list\/images\/casualty\/vikingskyap_19083030766106.png?rev=148d177acfae4ee28cd0feafe0cce2b0\" alt=\"https:\/\/www.lloydslist.com\/-\/media\/lloyds-list\/images\/casualty\/vikingskyap_19083030766106.png?rev=148d177acfae4ee28cd0feafe0cce2b0\" style=\"width:578px;height:auto\"\/><\/figure>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/www.foreship.com\/_thumbs\/wManage\/data\/userfiles\/images\/2000x2000_868033_Foreship%20website%20cover%20pic%20%287%29%281%29.png\" alt=\"https:\/\/www.foreship.com\/_thumbs\/wManage\/data\/userfiles\/images\/2000x2000_868033_Foreship%20website%20cover%20pic%20%287%29%281%29.png\"\/><\/figure>\n\n\n\n<p>In the <strong>MV <em>Viking Sky<\/em><\/strong> incident (Norway, March 2019), investigations showed that generator operation became unstable under heavy weather and dynamic load.<\/p>\n\n\n\n<p>Key points:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>generators were running<\/li>\n\n\n\n<li>load conditions changed rapidly<\/li>\n\n\n\n<li>stability margins disappeared<\/li>\n\n\n\n<li>multiple units tripped sequentially<\/li>\n\n\n\n<li>propulsion was lost<\/li>\n<\/ul>\n\n\n\n<p>While lubrication issues were the initiating factor, <strong>load sharing and recovery dynamics determined whether the ship survived<\/strong>.<\/p>\n\n\n\n<p>ETO lesson:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>Load sharing quality determines whether redundancy actually exists.<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">How load sharing fails in practice<\/h2>\n\n\n\n<p>Common onboard failure patterns:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>governor droop mismatches<\/li>\n\n\n\n<li>AVR droop incorrectly tuned<\/li>\n\n\n\n<li>PMS logic overridden for convenience<\/li>\n\n\n\n<li>generators paralleled outside design envelope<\/li>\n\n\n\n<li>no testing after maintenance<\/li>\n<\/ul>\n\n\n\n<p>Load sharing problems rarely announce themselves clearly. They <strong>surface under stress<\/strong>, when correction time is minimal.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Professional ETO mindset<\/h2>\n\n\n\n<p>A competent ETO doesn\u2019t ask:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u201cAre all generators online?\u201d<\/li>\n<\/ul>\n\n\n\n<p>They ask:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><em>Are they sharing both kW and kVAr correctly?<\/em><\/li>\n\n\n\n<li><em>Which unit will trip first if load spikes?<\/em><\/li>\n\n\n\n<li><em>What happens if that unit trips right now?<\/em><\/li>\n<\/ul>\n\n\n\n<p>Load sharing is not redundancy.<br><strong>Correct load sharing creates redundancy.<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Knowledge to Carry Forward<\/h2>\n\n\n\n<p>Parallel generators are cooperative systems. If they compete instead of cooperate, redundancy collapses into fragility.<\/p>\n\n\n\n<p>A PMS that cannot share load smoothly under real operating conditions will eventually create a blackout \u2014 usually at the worst possible moment.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Tags<\/h2>\n\n\n\n<p>ETO, Power Management System, Load Sharing, Generator Paralleling, Viking Sky, Marine Blackout, IEC 60092, SOLAS II-1, Ship Electrical Stability<\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Load Sharing \u2014 When Generators Fight Each Other Introduction \u2014 load sharing is where \u201chealthy\u201d systems quietly kill ships Many vessels lose power without any generator actually failing. Engines run, fuel is clean, cooling is normal \u2014 yet the ship blacks out. The cause is often poor load sharing. When generators are paralleled, they must [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"fifu_image_url":"","fifu_image_alt":"","c2c-post-author-ip":"","footnotes":""},"categories":[9,1],"tags":[],"class_list":["post-48237","post","type-post","status-publish","format-standard","hentry","category-electrical","category-latest"],"acf":[],"_links":{"self":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/48237","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fcomments&post=48237"}],"version-history":[{"count":1,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/48237\/revisions"}],"predecessor-version":[{"id":48241,"href":"https:\/\/maritimehub.co.uk\/?rest_route=\/wp\/v2\/posts\/48237\/revisions\/48241"}],"wp:attachment":[{"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fmedia&parent=48237"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Fcategories&post=48237"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/maritimehub.co.uk\/?rest_route=%2Fwp%2Fv2%2Ftags&post=48237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}